Loading calendars failed

Hi,

I’m using Nextcloud 14.0.3.0 on a Debian server. Several users are able to load and use the calendar app.

However, one user is reporting the following javascript error while trying to access the app calendar:

image

What could be wrong with this user data?

best,
alan

Are there any special characters in the user’s username? Are some calendars shared with them? Did they force refresh the page?