Syncronization with DAVx⁵ doesn't work properly

I've encountered an odd behaviour when using DAVx⁵ to synchronize my tasks.

I installed DAVx⁵ and added my Nextcloud account. All went smooth. DAVx⁵ showed my existing task lists. I even added a new Collection which now shows up in Nextcloud tasks. However when I open up jtx Board no tasks show up. And when I try to add a new task I can only select Local (Local). When I switch to Collections it shows me "No remote Collections found".

At first I thought that synchronization doesn't work at all. But that's when I noticed the following:

When I go to DAVx⁵ → <my account> → CALDAV and press the refresh button in the bottom right corner and switch back to the jtx Board app immediately it shows all my tasks for about half a second. After that they vanish again. Similarly if I switch back from DAVx⁵ to the Collections page in the jtx Board app all Remote Collections show up until I switch to another page and back to Collections.

Either I didn't set it up correctly or this is a bug. I would appreciate some input on this. Other than that this looks like a truly great app though.