Good day.
I found unexpected behavior of more event popup for device mode.
If I use fixed height of schedule and click
+n button in cell, more events popup appears with some negative value of
top style
https://stackblitz.com/edit/react-zbbdse-pq1hvs

I think internal logic takes height of screen (667px on sample) and height of scheduler (300px on sample) and do some calculation(like 300-667).
Anyway as workaround I can use
top:0!important but it's a bad practice.