Timecard - Holiday cannot be entered on a non-holiday - even though a Calendar event exists

Hi Team,

We are seeing a trend right after 25D as we are getting this error even though a Calendar event exist for few Holidays.
However, this is working good for other Calendar events in the very same Country.

But the strange thing is when we delete and re-entered the Calendar event, then it is working fine and not getting any error.

What could be the issue, how can we identify the issue for respective calendar events up front before colleagues raise an issue?
Do we have any diagnostic Test report or a process which can help us in this scenario? or any other solution?