@ Nader
I see you’re using a caching plugin, which one?
Connections 8.1 introduced fragment caching. This is the process of caching process/memory intensive options. The only place at this time that uses fragment caching are the categories in the admin.
This fragment caching utilities the core WordPress Transient API. Third party caching plugins can alter the behavior, genreally to use a faster caching method.
My guess is the caching plugin is not clearing the Connections fragment caches when requested which in Connections case would be when an entry is added/edited or a category is added/edited.
Can you please try deactivating the the caching plugin to see if the issue goes away? If it does and I suspect it will, can you please attach screen captures of all the caching plugins settings pages so I can attempt to duplicate the issue?
