@MrGutsy It should be possible to set up the account with the working connection (4G) and then sync over WiFi, too.
Tasks description isn't synced
It seems that the description field of Tasks isn’t synced.
I’m using Tasks, DAVdroid and Owncloud in my setup, so I’m not sure where the problem is but it might be in DAVdroid as suggested by Tasks dev:
Ok, thanks. I’ll take a closer look into this. It actually might be something else that’s broken because I don’t see the problem in a simple case, so I’ll close this for now and examine it in more detail.