Subcategories are not displayed correctly

[miga81]

Hello together,

first of all my system information:

Joomla 3.10
mySQL 5.5.45
PHP 7.4.13
jDownloads 3.9.2

I have the problem, that some subcategories aren't displayed. They are not empty and I don't regognize a pattern why some subcategories are displayed and some aren't. Also If I add a test subcategory the behaviour of the list changes. In the dropbox menu all subcategories are listed and I can select them, but in the folder list there are no entries.

Do someone have an advice?

Best regards,
Michael