P106 Hashrate drop problem with Claymore Miner

Hi,
Sorry for the bad English.
I am using 12x P106-090 Manli brand. (6GB 192 Bit Samsung GDDR5 Memory With 5SM GPU)
The Manli website states that it is 21-22MH / s, but I can't exceed 16MH / s with Windows 1903 and HiveOS, and if I overclock, my speed doesn't increase above 16MHs. I have tried the most up-to-date nVidia 430.50 WHQL and Manli with the original stock driver. I downloaded P106-100 REV 1 driver from Gigabyte and the problem persisted. I completely uninstalled the drives with DDU, tried with Phoenixminers 4.7c and old version.
disabled driver signatures. Where's the problem? Please help me and thank you very much.