Does this help?
Not specifying --cpu-affinity:
[2019-06-04 01:29:03] 56 CPU cores available, 30 miner threads selected.
[2019-06-04 01:29:03] Starting Stratum on stratum+tcp://***
[2019-06-04 01:29:03] Binding thread 0 to cpu 0 (mask 1)
[2019-06-04 01:29:03] Binding thread 14 to cpu 14 (mask 4000)
[2019-06-04 01:29:03] Binding thread 9 to cpu 9 (mask 200)
[2019-06-04 01:29:03] affine_to_cpu_mask for 9 returned 57
[2019-06-04 01:29:03] Binding thread 4 to cpu 4 (mask 10)
[2019-06-04 01:29:03] Binding thread 18 to cpu 18 (mask 40000)
[2019-06-04 01:29:03] Binding thread 7 to cpu 7 (mask 80)
[2019-06-04 01:29:03] affine_to_cpu_mask for 7 returned 57
[2019-06-04 01:29:03] 30 miner threads started, using 'yescrypt' algorithm.
[2019-06-04 01:29:03] Binding thread 22 to cpu 22 (mask 400000)
[2019-06-04 01:29:03] Binding thread 6 to cpu 6 (mask 40)
[2019-06-04 01:29:03] Binding thread 2 to cpu 2 (mask 4)
[2019-06-04 01:29:03] Binding thread 11 to cpu 11 (mask 800)
[2019-06-04 01:29:03] affine_to_cpu_mask for 11 returned 57
[2019-06-04 01:29:03] Binding thread 8 to cpu 8 (mask 100)
[...]
Specifying --cpu-affinity=0xd555555d555555:
[2019-06-04 01:30:37] 56 CPU cores available, 30 miner threads selected.
[2019-06-04 01:30:37] Starting Stratum on stratum+tcp://***
[2019-06-04 01:30:37] Binding thread 0 to cpu mask 35ffbe0
[2019-06-04 01:30:37] Binding thread 7 to cpu mask 43ffbe0
[2019-06-04 01:30:37] Binding thread 9 to cpu mask 47ffbe0
[2019-06-04 01:30:37] Binding thread 10 to cpu mask 49ffbe0
[2019-06-04 01:30:37] Binding thread 4 to cpu mask 3dffbe0
[2019-06-04 01:30:37] Binding thread 19 to cpu mask 5bffbe0
[2019-06-04 01:30:37] Binding thread 6 to cpu mask 41ffbe0
[2019-06-04 01:30:37] 30 miner threads started, using 'yescrypt' algorithm.
[2019-06-04 01:30:37] Binding thread 1 to cpu mask 37ffbe0
[2019-06-04 01:30:37] Binding thread 8 to cpu mask 45ffbe0
[2019-06-04 01:30:37] Binding thread 2 to cpu mask 39ffbe0
[2019-06-04 01:30:37] Binding thread 11 to cpu mask 4bffbe0
[2019-06-04 01:30:37] Binding thread 12 to cpu mask 4dffbe0
[2019-06-04 01:30:37] Binding thread 13 to cpu mask 4fffbe0
[2019-06-04 01:30:37] Binding thread 3 to cpu mask 3bffbe0
[...]
Those CPU masks become quite weird with --cpu-affinity. And in the end, it's actually bound to CPUs 0-31.