And more reports. It is now clear that the problem is still there and it _only_ happens shortly after a devfee session, hence it strongly suggests that the problem is linked to the devfee, note the stream of dupes after some devfee sessions below ... 9 out of 700 shares is more than 1% loss of hashrate:
# grep -P 'session|Acc|Rej' /l|grep -P 'session' -A 20
wolf [13:51:46] INFO - Start user session
wolf [13:53:23] INFO - 1/0 Accepted : diff=9707131 : 66.73KH/s
wolf [13:53:31] INFO - 2/0 Accepted : diff=3967112 : 68.71KH/s
wolf [13:53:48] INFO - 3/0 Accepted : diff=4547175 : 69.58KH/s
wolf [13:54:04] INFO - 4/0 Accepted : diff=2685536 : 69.88KH/s
wolf [13:54:55] INFO - 5/0 Accepted : diff=6598524 : 70.01KH/s
wolf [13:56:28] INFO - 6/0 Accepted : diff=7312975 : 70.14KH/s
wolf [13:56:29] INFO - 7/0 Accepted : diff=10894511 : 70.15KH/s
wolf [13:56:36] INFO - 8/0 Accepted : diff=2946288 : 70.15KH/s
wolf [13:56:41] INFO - 9/0 Accepted : diff=299441026 : 70.13KH/s
wolf [13:57:26] INFO - 10/0 Accepted : diff=39524063 : 70.14KH/s
wolf [13:59:45] INFO - 11/0 Accepted : diff=8553147 : 70.16KH/s
wolf [14:00:55] INFO - 12/0 Accepted : diff=4701975 : 70.17KH/s
wolf [14:02:03] INFO - 13/0 Accepted : diff=3705832 : 70.19KH/s
wolf [14:02:07] INFO - 14/0 Accepted : diff=7194491 : 70.18KH/s
wolf [14:02:43] INFO - 15/0 Accepted : diff=9761342 : 70.19KH/s
wolf [14:03:05] INFO - 16/0 Accepted : diff=5269496 : 70.19KH/s
wolf [14:03:08] INFO - Start devfee session
wolf [14:03:43] INFO - Start user session
wolf [14:04:08] INFO - 17/0 Accepted : diff=2845616 : 70.19KH/s
wolf [14:04:30] INFO - 18/0 Accepted : diff=6288420 : 70.19KH/s
wolf [14:04:31] INFO - 19/0 Accepted : diff=8576415 : 70.19KH/s
wolf [14:05:19] INFO - 19/1 Rejected : diff=8553147, reason: Duplicate share2
wolf [14:05:58] INFO - 20/1 Accepted : diff=14668108 : 70.19KH/s
wolf [14:06:24] INFO - 21/1 Accepted : diff=2694462 : 70.19KH/s
wolf [14:06:57] INFO - 22/1 Accepted : diff=2706372 : 70.19KH/s
wolf [14:07:54] INFO - 23/1 Accepted : diff=4550410 : 70.20KH/s
wolf [14:08:32] INFO - 24/1 Accepted : diff=22443368 : 70.20KH/s
wolf [14:08:59] INFO - 25/1 Accepted : diff=15335047 : 70.20KH/s
wolf [14:09:30] INFO - 26/1 Accepted : diff=5348687 : 70.19KH/s
wolf [14:09:51] INFO - 27/1 Accepted : diff=5098150 : 70.20KH/s
wolf [14:09:55] INFO - 28/1 Accepted : diff=6124693 : 70.20KH/s
wolf [14:10:34] INFO - 29/1 Accepted : diff=2684823 : 70.19KH/s
wolf [14:10:35] INFO - 30/1 Accepted : diff=6696221 : 70.20KH/s
wolf [14:10:48] INFO - 31/1 Accepted : diff=3087039 : 70.20KH/s
wolf [14:12:01] INFO - 32/1 Accepted : diff=6521047 : 70.20KH/s
wolf [14:12:36] INFO - 33/1 Accepted : diff=2974587 : 70.20KH/s
wolf [14:13:02] INFO - 34/1 Accepted : diff=5026248 : 70.20KH/s
wolf [14:14:58] INFO - 35/1 Accepted : diff=4915106 : 70.20KH/s
--
wolf [15:01:09] INFO - Start devfee session
wolf [15:01:44] INFO - Start user session
wolf [15:01:50] INFO - 108/1 Accepted : diff=8045525 : 70.21KH/s
wolf [15:02:13] INFO - 109/1 Accepted : diff=3844769 : 70.21KH/s
wolf [15:04:02] INFO - 110/1 Accepted : diff=7749041 : 70.21KH/s
wolf [15:04:27] INFO - 111/1 Accepted : diff=70845897 : 70.21KH/s
wolf [15:05:58] INFO - 112/1 Accepted : diff=2787856 : 70.21KH/s
wolf [15:06:12] INFO - 113/1 Accepted : diff=3263759 : 70.21KH/s
wolf [15:06:18] INFO - 114/1 Accepted : diff=3381829 : 70.21KH/s
wolf [15:06:40] INFO - 115/1 Accepted : diff=6786242 : 70.21KH/s
wolf [15:07:13] INFO - 116/1 Accepted : diff=2733179 : 70.21KH/s
wolf [15:07:17] INFO - 117/1 Accepted : diff=13263367 : 70.21KH/s
wolf [15:07:28] INFO - 118/1 Accepted : diff=2710339 : 70.21KH/s
wolf [15:07:39] INFO - 119/1 Accepted : diff=2513194 : 70.21KH/s
wolf [15:07:47] INFO - 120/1 Accepted : diff=4316701 : 70.21KH/s
wolf [15:08:28] INFO - 121/1 Accepted : diff=3346370 : 70.21KH/s
wolf [15:08:40] INFO - 122/1 Accepted : diff=3320770 : 70.21KH/s
wolf [15:09:53] INFO - 123/1 Accepted : diff=3031607 : 70.21KH/s
wolf [15:11:29] INFO - 124/1 Accepted : diff=5589992 : 70.21KH/s
wolf [15:12:40] INFO - 125/1 Accepted : diff=15209899 : 70.21KH/s
wolf [15:13:40] INFO - 126/1 Accepted : diff=3867154 : 70.21KH/s
wolf [15:13:46] INFO - 127/1 Accepted : diff=12312207 : 70.21KH/s
--
wolf [15:59:11] INFO - Start devfee session
wolf [15:59:46] INFO - Start user session
wolf [15:59:46] INFO - 229/1 Accepted : diff=36833371 : 70.21KH/s
wolf [15:59:53] INFO - 229/2 Rejected : diff=71057445, reason: Duplicate share2
wolf [16:00:08] INFO - 230/2 Accepted : diff=30030473 : 70.21KH/s
wolf [16:00:18] INFO - 231/2 Accepted : diff=3413753 : 70.21KH/s
wolf [16:01:33] INFO - 232/2 Accepted : diff=5039366 : 70.21KH/s
wolf [16:01:59] INFO - 233/2 Accepted : diff=23368668 : 70.21KH/s
wolf [16:02:15] INFO - 234/2 Accepted : diff=4706655 : 70.21KH/s
wolf [16:02:55] INFO - 235/2 Accepted : diff=8716313 : 70.21KH/s
wolf [16:03:19] INFO - 236/2 Accepted : diff=2590195 : 70.21KH/s
wolf [16:04:19] INFO - 237/2 Accepted : diff=2623047 : 70.21KH/s
wolf [16:04:39] INFO - 238/2 Accepted : diff=12238986 : 70.21KH/s
wolf [16:04:59] INFO - 239/2 Accepted : diff=3338505 : 70.21KH/s
wolf [16:05:03] INFO - 240/2 Accepted : diff=3999826 : 70.21KH/s
wolf [16:05:50] INFO - 241/2 Accepted : diff=4975893 : 70.21KH/s
wolf [16:05:55] INFO - 242/2 Accepted : diff=3999277 : 70.21KH/s
wolf [16:07:06] INFO - 243/2 Accepted : diff=3956594 : 70.21KH/s
wolf [16:07:14] INFO - 244/2 Accepted : diff=3583551 : 70.21KH/s
wolf [16:07:18] INFO - 245/2 Accepted : diff=4571742 : 70.21KH/s
wolf [16:07:40] INFO - 246/2 Accepted : diff=3130914 : 70.21KH/s
wolf [16:08:28] INFO - 247/2 Accepted : diff=3391861 : 70.21KH/s
--
wolf [16:57:13] INFO - Start devfee session
wolf [16:57:48] INFO - Start user session
wolf [16:58:13] INFO - 347/2 Accepted : diff=13060685 : 70.12KH/s
wolf [16:58:19] INFO - 348/2 Accepted : diff=12609630 : 70.12KH/s
wolf [16:58:44] INFO - 349/2 Accepted : diff=3408431 : 70.12KH/s
wolf [16:58:48] INFO - 350/2 Accepted : diff=3239141 : 70.12KH/s
wolf [16:59:46] INFO - 351/2 Accepted : diff=2120311 : 70.12KH/s
wolf [17:00:00] INFO - 352/2 Accepted : diff=3220798 : 70.12KH/s
wolf [17:00:01] INFO - 353/2 Accepted : diff=1743769 : 70.12KH/s
wolf [17:00:17] INFO - 354/2 Accepted : diff=4832606 : 70.12KH/s
wolf [17:00:26] INFO - 355/2 Accepted : diff=2758301 : 70.12KH/s
wolf [17:00:29] INFO - 356/2 Accepted : diff=19267812 : 70.12KH/s
wolf [17:00:40] INFO - 357/2 Accepted : diff=4746679 : 70.12KH/s
wolf [17:00:55] INFO - 358/2 Accepted : diff=1994282 : 70.12KH/s
wolf [17:00:56] INFO - 359/2 Accepted : diff=1611069 : 70.12KH/s
wolf [17:02:28] INFO - 360/2 Accepted : diff=2696282 : 70.12KH/s
wolf [17:02:44] INFO - 361/2 Accepted : diff=1877291 : 70.12KH/s
wolf [17:03:01] INFO - 362/2 Accepted : diff=5103530 : 70.12KH/s
wolf [17:03:25] INFO - 363/2 Accepted : diff=2747869 : 70.12KH/s
wolf [17:03:38] INFO - 364/2 Accepted : diff=2523963 : 70.12KH/s
wolf [17:03:57] INFO - 365/2 Accepted : diff=1834063 : 70.12KH/s
wolf [17:04:03] INFO - 366/2 Accepted : diff=1519501 : 70.12KH/s
--
wolf [17:55:15] INFO - Start devfee session
wolf [17:55:50] INFO - Start user session
wolf [17:56:26] INFO - 510/3 Rejected : diff=5860670, reason: Duplicate share2
wolf [17:56:33] INFO - 511/3 Accepted : diff=2079824 : 70.14KH/s
wolf [17:56:36] INFO - 511/4 Rejected : diff=1751280, reason: Duplicate share2
wolf [17:56:40] INFO - 512/4 Accepted : diff=2622487 : 70.14KH/s
wolf [17:57:00] INFO - 513/4 Accepted : diff=1600533 : 70.14KH/s
wolf [17:57:20] INFO - 514/4 Accepted : diff=1731885 : 70.14KH/s
wolf [17:58:54] INFO - 515/4 Accepted : diff=2186328 : 70.14KH/s
wolf [17:59:30] INFO - 516/4 Accepted : diff=36416857 : 70.14KH/s
wolf [17:59:37] INFO - 517/4 Accepted : diff=4543109 : 70.14KH/s
wolf [17:59:40] INFO - 518/4 Accepted : diff=1998386 : 70.14KH/s
wolf [17:59:54] INFO - 519/4 Accepted : diff=3210560 : 70.14KH/s
wolf [17:59:59] INFO - 520/4 Accepted : diff=13430242 : 70.14KH/s
wolf [18:00:09] INFO - 521/4 Accepted : diff=8094012 : 70.14KH/s
wolf [18:00:33] INFO - 522/4 Accepted : diff=7677224 : 70.14KH/s
wolf [18:01:05] INFO - 523/4 Accepted : diff=2859943 : 70.14KH/s
wolf [18:01:06] INFO - 524/4 Accepted : diff=1502524 : 70.14KH/s
wolf [18:01:28] INFO - 525/4 Accepted : diff=5087552 : 70.14KH/s
wolf [18:01:35] INFO - 526/4 Accepted : diff=2255076 : 70.14KH/s
wolf [18:01:49] INFO - 527/4 Accepted : diff=3009946 : 70.14KH/s
wolf [18:02:23] INFO - 528/4 Accepted : diff=3676582 : 70.14KH/s
--
wolf [18:53:17] INFO - Start devfee session
wolf [18:53:51] INFO - Start user session
wolf [18:54:03] INFO - 690/4 Accepted : diff=1938546 : 70.15KH/s
wolf [18:54:34] INFO - 691/4 Accepted : diff=80352040 : 70.15KH/s
wolf [18:54:35] INFO - 692/4 Accepted : diff=2279346 : 70.15KH/s
wolf [18:55:32] INFO - 692/5 Rejected : diff=3190294, reason: Duplicate share2
wolf [18:55:47] INFO - 693/5 Accepted : diff=3159834 : 70.15KH/s
wolf [18:55:55] INFO - 694/5 Accepted : diff=1847205 : 70.15KH/s
wolf [18:55:56] INFO - 695/5 Accepted : diff=3163183 : 70.15KH/s
wolf [18:56:25] INFO - 695/6 Rejected : diff=1615478, reason: Duplicate share2
wolf [18:56:35] INFO - 696/6 Accepted : diff=2337701 : 70.15KH/s
wolf [18:56:38] INFO - 696/7 Rejected : diff=2910962, reason: Duplicate share2
wolf [18:57:07] INFO - 697/7 Accepted : diff=7064794 : 70.15KH/s
wolf [18:57:09] INFO - 697/8 Rejected : diff=3403047, reason: Duplicate share2
wolf [18:57:09] INFO - 698/8 Accepted : diff=1671493 : 70.15KH/s
wolf [18:57:34] INFO - 699/8 Accepted : diff=3104612 : 70.15KH/s
wolf [18:57:37] INFO - 700/8 Accepted : diff=4688695 : 70.15KH/s
wolf [18:58:19] INFO - 700/9 Rejected : diff=11600888, reason: Duplicate share2
wolf [18:58:25] INFO - 701/9 Accepted : diff=3900978 : 70.15KH/s
wolf [18:58:32] INFO - 702/9 Accepted : diff=3917767 : 70.15KH/s
wolf [18:59:24] INFO - 703/9 Accepted : diff=43616531 : 70.15KH/s
wolf [19:00:57] INFO - 704/9 Accepted : diff=1836569 : 70.16KH/s