I need to know Windows version, GPU model and drivers version to be able to reproduce this issue.
My specs:
Windows 10 x64 Enterprise - BUILD 10240
Driver - AMD blockchain Beta driver driver, 23 aug (windows driver version 22.19.659.0)
GPUs:
1x ASUS DUAL 480 4GB
1x Sapphire 470 Nitro+ 4GB
3x MSI 750 Armor OC 4GB
They all exhibit the changing clock/voltage -> lower performance until reboot issue that IMO is ADL related (as it happened always for me with Polaris GPUs, not only with mining, general use and gaming too, you can even see how the bandwidth is cut with AIDA or other bw gpu bench when you alter settings at least on windows with polaris GPUs).
The x25mv x50mv x75mv x00mv only voltage issue is a deduction of mine after seeing the gpu instant hang when using other voltages than these ones on the ASUS DUAL 480 4GB.