All I can say is that after logging in, the graphics of the game get messed up. Can find the image of what happens here. I am running on Mac OS X 10.15 (19A558d), MacBook Pro 15, mid 2018 model and using the new 64 bit game client.
This glitch look like graphic memory corrupted, last time i have this issue (similare) it was the memory ram on the graphic board who was one ram with problem. It was not on all game, just when some data was in the specific adress.
But maybe it's not that
Were you able to solve the glitch issue?
I just experienced the exact same issue and use a MBP 2016. Could you solve it?
I just managed to go to the settings to activate the "window" mode. no problems there.