I have two identical cards, Asus Strix rx580 oc 8gb Samsung memory modded bios with Ubermix 3.1 straps on 2000 and 1750. One is working perfectly fine on stock speeds. Other one getting some memory errors, and after about 1h, hashrate on it slowly begins to drop. When i downclock memory from 2000 to 1950, it works fine, without memory errors, but hashrate is 1 mhs lower compared to the other one without problems. I did try to copy 1750 to 2000 strap, Ubermix less extreme 2.3, same thing happens.

Is there any other way to do something about it? Their memory quality is just different or i'm missing something?

Didn't touched anything about power and voltage so far.

your Polaris Bios Editor 1.6.2 link, stinks.