Thank you that is a good start for me.
build from source with local ical4j
I already know this problem from ICal import export app which also uses ical4j. Reinstalling only helped for a few days.
In order to try to debug this I would like to build DavX5 and ical4j from source with added debug info and perhaps assertions.
As I don’t have experience with the build process in Android Studio i would like to know how I can change the build for DavX5 such that it uses the locally built ical4j. Where can I change this and which files from the ical4j build do I need?
Unfortunately, it’s not that easy. I guess you would have to exclude the dependency ical4j from ical4android and include a new submodule (= the downloaded local ical4j) instead.