same here
179MH become 167MH
try set -daglim 4076, i have 474/574 cards, PM 5.2d, win10 1703, drivers 19.6.2, if -daglim 1 (auto, 4023) hashrate about 167MH/s, if set -daglim 4031-4076 hashrate is normal 180Mh, as before
yeah. not really sure what's up, but all my 4gb polarises (except last devices at 10+) now hashing as they were