Propagated events not merging (Manual event Merge option)

On Desktop - certain random propagated calendar events are not merging with the source calendar event even with "Merge Duplicate Events" enabled.

On Mobile - For source events that I have propagated across more than one calendar, the propagated events merge with each other but not with the source event. I am using a Pixel 8 (has same issue with my Pixel 6a) and using the latest version of Android. It only seems to work correctly for a very small % of events.