Unable to change participants from who field in Team Calendars

Summary

When attempting to modify events in Team Calendar for Confluence who field changes are not respected

Environment

• Confluence Data Center
• Team Calendar for Confluence 5.5.0 or 6.0.14

Steps to Reproduce

1. Create an event in Team Calendars
2. Add users to Who field
3. Save Event
4. Edit event and try removing Users from Who field

Expected Results

• Users removed and event updated

Actual Results

• Either some users get removed or no changes are observed

Clearing plug-ins cache and re-indexing from scratch has no effect on the issue.

atlassian-confluence.log has the following events logged

WARN [http-nio-6710-exec-10] [extra.calendar3.util.TimeZoneUtil] tryParseDateTimeStringForEventEdit Unable to parse date null

Workaround

There is no workaround