Is there a way to revert to prior settings to avoid 'Not Responding' after starting Thunderbird

Hi. On Windows 11. after adding an ical calendar, Thunderbird immediately stops responding. If I then stop and restart Thunderbird it continues to not respond. 1. Is there a simple way to revert to the state prior to the addition of the calendar? Or can a point of consistency be established prior to adding the calendar to make reverting to this point a possibility? 2. I presume that there is some issue with the contents of the ical. Is there any way to work out what might be the issue that Thunderbird is not handling? The calendar is a Google Calendar and works fine there. Thanks in advance.