I am playing WoW Classic TBC anniversary on Nightslayer. Doesn’t matter the character name it happens on any of my characters. When I log on I have to sit and wait for 3-5 minutes while the game just flickers and what I see on the screen jumps between the bottom of the map and a black screen. It also lags my entire computer. Happens whether or not I have addons turned on. Also once I have done this once as long as I don’t close the game completely I can swap to any of my other characters just fine.
Edit:
Swapped to DX11 seems to bypass this issue.