This bug usually affects some AMD GPUs. I have a fix for it, but forgot to apply it to the offending transition in the part of the game you talk about, so I'll be fixing it in 0.21
In the meantime, press shift-g in the game, and change the renderer to ANGLE2, then relaunch the game. This fixes the problem for most people. (Let me know if that works)
Sory for late reply. There was no notification for some reason.