[2018-07-28 17:05:26] : Result accepted by the pool.
RESULT REPORT
Difficulty       : 100001
Good results     : 1374 / 1378 (99.7 %)
Avg result time  : 18.4 sec
Pool-side hashes : 137401374

Top 10 best results found:
|  0 |         36059249 |  1 |         28015159 |
|  2 |         20688899 |  3 |         13746335 |
|  4 |         11451266 |  5 |         10730227 |
|  6 |          9963080 |  7 |          9945617 |
|  8 |          9792294 |  9 |          9617152 |

Error details:
| Count | Error text                       | Last seen           |
|     4 | Rejected share: invalid result   | 2018-07-28 15:49:17 |



So it seems my problem with the rejected shares was having the cpu.txt config set to use  ""low_power_mode" : true".
Also tested in a VM, the cpu config was set to ""low_power_mode" : true" , which was the default that xmr-stak auto config set, I had tons of invalid shares. When I set it to ""low_power_mode" : false" no invalid shares for the short test I did.

This is in Ubuntu 16.04.4 and xmr-stak 2.4.7