Hashrate jump

[Pushking90]

Hello. I'm using rigs with rx 474. Rigs with 1150/1156/1155 got stable hashrate which drop every epoch, but it is fine and logically. On am4 rig (tried different cpus/ram/power supply i got unstable hashrate in fact that rave os shows stable (everything gen3). So first 15-30 mins it shows in miner log and on rave os website 27.8 mh/s. But later miner log shows slow jumps from 24 to 27.5 mh/s. During this time rave os still shows hashrate 27.7-27.9. i tried to tank down OC, changed +- core and mem voltage, tried different 4gallocsize arguments, but every time after 15-20 mins it jumps... Im thinking about buying new 474 rigs but this situation stops me ;( any suggestions? Thanks.
P.s. zombie mode auto or 12-15. Doesn't metter...

[Pushking90]

Asus rog strix b450-E
Ryzen 3600
Kingston hyperx 3200cl16 2*16gb
Tried on asus tuf b450 gaming pro
Ryzen 3100/3600
Same ram.
Same situation...