Hi,

I can also report high % of stales / rejected (>10%) with RX 6600XT with Phoenix 5.7b

With NBMiner 39.0 only about 0.05% stales/rejected.

OS:     Windows 10 Version 2009, 10.0.19043
Driver: non-whql-radeon-software-adrenalin-2020-21.8.1-win10-64bit-aug10