I am using Xubutu 20.04. I have observed that there might be some error in the Thunar File Manager. When I visit my videos folder, it creates thumbnails for first few rows, and then stops. I've tried reseting it by deleting the folder at ./config , but it doesn't seem to reset the file manager. However, when I restart my system, it works flawless, for few minutes, but again stops generating thumbnails.
Edit: It actually stops generating thumbnails for the folders of the entire system!