Hi Yi,
I have the same issue and this appeared after downloading extra grunge maps in separate folder with same name as the default grunge maps. I thought about reinstalling the software and not using the extra grunge maps, since I am not sure what would happen to the dependencies if I rename them? I have been off an on with SD for some time now and mostly used bitmaps to get materials. Plans are to finally spend some time to learn the program for real, and I cannot say for sure if the above is what caused it? The rebuild of images seems to work here and there, then I reopen and find many missing.
I also tried reducing dpi and all of the suggestions here. Nothing really works when I come back they are still missing.
Computer I am using is:
windows 10
quadro rtx max q 5000
Intel(R) Xeon(R) E-2276M CPU @ 2.80GHz 2.81 GHz
Latest drivers nvidia