LR 13.3 previews not showing/built if no develop preset

[IngbertG]

Hi,

lately I noticed that LR doesnt show previews in the library module for many of my photos. It did not even build them without "force" - I had to select the image and then after some time, the preview was built.

I deleted the complete preview folder, but the problem persisted. SOME photos got their preview rebuild nearly instantly when I scrolled through the library, others refused to show their preview. Task manager showed LR idling at 0.5 to 0% CPU (and I DO have a nice machein!)

Playing around I at least found WHICH images are the problem: Metadata -> Develop presets. ALL images WITH (any) develop preset work as exprected, previews created ultra fast. All image without preset have problems with preview.

Questions:

1. Anybody else with this problem?
2. Any "workaround"? Like adding a "dummy" preset to all images with no preset?
3. Is it a bug or something corrupted in my catalog?

[JohanElzenga]

A preset does nothing except setting a few sliders for you, so you don't have to manually do that each time. I don't see how  not having applied a 

preset could possibly be the cause of thumbnails not showing. I think it is more likely that the real cause is a defective monitor profile. That is known to cause thumbnails not to show.