Premiere Pro 2020 - After Adding clip to timeline, stuck white preview screen

If I am dragging a already importet clip into the timeline, the preview windows will get white or black and if i playback, I am hearing th esound correctly (MME) but the Cursor in the timeline will not move and no clip is beeing shown in the preview window.

at the moment my workaroud is to change the workspace, save the project and reopen premiere, but it is anoying and doesnt work all the time, it cant be the soultion.

deleting trash files didnt help.

also it is on coposite video

same problem with CC 2019 and 2020

oh, another issue: if the white screen exists and i am trying to close premiere, the GUI will close but a process will run in the backgroud (and the windows menue isn't working)

Hardware:

- Intel i9-9900k.@4,79GHz

- 32GB DDR4 RAM

- tryied different SSDs / m.2 SSDs

- nvidia RTX 2080 TI with 4 different monitors.

(windows 10 1903, setup on april, 2019)

maybe somebody has an idea

i am sorry if this issue was already solved, but i didnt find anything

i hope i didnt forgot anything in this post (and my englisch ist not so bad)

in the photo you see the white prieview window, but it is playback and you can see the volume master, because sound work properly