Zusätzliche kalenderbezogene Funktionen und Probleme innerhalb von Microsoft Teams for Business
I experienced the same issue some weeks ago. It started with a unreliable behavior. For some exports the description column was exported properly, for some exports it was empty. Now it always fails.
Today I found something new: Teams just exports the descriptions which I have adapted recently. So I just entered all single descriptions, set a space character at the end of the text and closed the task. This is of course still a bug and not a future solution, but I wanted to share this finding anyway.