Thanks for your quick reply.
I'll see what I can do regarding upgrading my Android version. Bad news is that support for my phone has been dropped about a week ago, so I won't have a(n official) upgrade path.
There is an unofficial Kitkat build for my phone, which I might check out.
I'd be very grateful if you could fix the issue I've encountered. As I said before, I never had any problems with DAVdroid before (except for some small issues that were always fixed 1 or 2 releases after I've encountered the bugs).
Would you like me to create new bug reports if I encounter problems in the future or do you consider issues I might have WONTFIX because of my outdated Android version?
I don't mind reporting any future issues, but I don't want to spam the forum with reports that won't get fixed anyway. That's a waste of both your time and mine.