Trying to fully delete an image and dialog looks like this. I can mouse over to the “delete” button and then I can see it.
I have experienced something similar to this on Linux. Most often when opening the settings window. Sometimes it was totally black and other times only part of the window was black, as you experienced. Waving the mouse pointer over the black area made visible some or all of the elements, but not always. It seemed to do this while the program was under a heavy workload. I have not had much of an issue with this since preview-38 was released.
The main drawn area looks suspiciously close to half of the dialog. For that reason I would suspect that there might be a brief moment where the correct scale factor for the window hasn’t yet been properly propagated. I’ll have a look whether I can find something, or whether I can reproduce this with with a background workload.
Edit: tracked as #1393
Got it to reproduce and made a fix for preview 39.
Awesome!