@UksusoFF Can’t reproduce that here. Are there any crash details? Do you use OpenTasks? Did you install it before DAVdroid? Which operating system/version do you use? Is there a privacy guard active? Did you disable system apps like the calendar or contacts storage?
More information is required to get an idea what the problem is. Also, please provide debug info.
Maybe it’s a database concurrency problem. I have sometimes received such crash reports, but only for Android 4.0.x (probably because its SQLite doesn’t support WAL yet) and I was never able to reproduce such a problem.