Hello again,
I just updated all the plugins to the latest versions.
The issue you had found is resolved: when nothing is supposed to be displayed, it doesn't show anything anymore (although it might be a good idea to instead display a text "No posts to show" or something of the sort? Just an idea).
However, this hasn't resolved my issue completely, as some filters should definitely still show something but they don't. For example:
My test account is connected with my admin account. My admin account has made a post on the forum.
When logged in with my test account and just using the standard filter "All", the forum post of my admin account appears without a problem. So when I go to the filter "Forum Posts", that same post should still appear. But it doesn't, it just shows no posts.
The settings I have for this filter are:
Filter: Forum Posts
Assets: kunena.%
Users: connections
Access: Registered
The same goes for filters like "Group Posts", "Gallery Posts" and "Wall Posts". Also on my admin account, which has nearly 2000 connections with inevitably some activity related to groups, gallery or just the wall itself, these filters show nothing. All of them, they are using the parameter "connections" for "Users". The filters that work with other parameters (such as "My Forum Posts" with [user_id]) does appear to work fine.