Good afternoon, doctor. I have a 13-card rig.
1) 9 cards of Sapphire RX550 / 2Gb on baffin
2) 1 card of Sapphire RX550 / 2 Gb on gfx804
3) 3 cards of MSI AERO RX550 / 2 GB on gfx804

On version 1.6.0, all cards worked with parameters 26.3 / 12 and issued:
1) at 497 h/s
2) 498 h/s
3) at 513 h/s

to my great regret at the transition to 1.6.1, and now on 1.6.2 with the same parameters of the cards began to give different results. In particular
The cards from point (1) remained at the same values, and from point (2) and (3) began to jump from 410 to 480 h/s. By reducing the parameters to 22.1/12 I was able to achieve a stable speed on the MSI cards from (3)  of 499 h/s, but could not achieve an acceptable speed on the card from point (2). I went through all the intensity options from 18 to 28 in steps of 0.1 the maximum stable result was reached at 22.1 / 12 at 475 h/s.