No parent page thumbnails in the pagepanel in Indesign 20.1

[maartenr49348889]

There are no parent page thumbnails in the pagepanel in Indesign 20.1. 
Still, “show thumbnails” is checked in the panal options. 

Is this a bug?

[maartenr49348889]

I solved this problem by removing the cachefiles of Indesign. 

Go to this folder and remove it:  Bibliotheek/Caches/Adobe InDesign
Restart Indesign and the tumbnails of the parent-pages are back in the page-panel. 

[Mike Witherell]

True. Most of the time, problems with missing parts of the interface mean the cache files are corrupt.

For the sake of other readers with a similar problem, here is a troubleshooting compendium.