I just installed the whole PG 64bit caboose, 2019 v 602 AP NEW. Apart from some buggies (like VST64bit not doing what i think it should) i found all quite stable, and the style picker refreshing with all the user styles collected over the years being quite slow, but there seem no Stylepicker problems.

Maybe a graphics issue om youw PC?: With windows 10 you never know whats up. I have 64bit pro 1803, BTW was told to tay away from 1809(6?), and switched off automatic windows updates, with a tool to make sure it stays off. Updated all the VCbasics both 32bit ANd 64bit, and DotNET 4.72. Can also be your graphics card drivers, as Microsoft changed stuff in Windows once again influencing those .... F