The issue with your .ics file appears to be in the UID field. Both events have the same UID (6335d25d9ecb2c).

In iCalendar files, the UID is supposed to uniquely identify each event. When multiple events share the same UID, some calendar applications (like Gmail desktop) interpret them as versions of the same event rather than separate events.

Note: Make sure each event has a unique UID value

UID:6335d25d9ecb2c

Change anyone's UID.