I have this strange wattman bug with my vega 64 where i have to close wattman from the taskbar before it sets the right changes to get a higher hashrate.
I do all the changes, lower the clockspeed to 1002, up the memory to 1100, power limit -24 etc.. apply changes and 38.5 is the highest i get.. up from about 31 at default, but when i close wattman from the taskbar and just keep it going in the background it suddenly ups the hashrate from 38 to 43.
*edit* mining ethereum with claymore that is.