yes, but of course this would not have been a good solution Anyway, now the problem has been fixed in the code, so this won't come back. Thank you for your help!

yup, this one is not an unknown one: got hit by it a few days ago. this situation is handled correctly in a few cases but not in others (so the fix can be trivial, but I want to make it generic and clean)

To fix in the interim: you can redo the actions (i.e. asking for the creation of calendars on Google) until Google cooperates. Usually on the second try everything goes well. A more definitive fix will come up in the next release (I still don't know whether it will be a major release with GUI, or just a bugfix release).