A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data
Tin,
I am an IT director for the company I work for. The "different environment" you are referring is inconsiquential. I have the same issue being reported on multiple systems, displays, keyboard and mouse combo's and etc. I also see the issue on Mac's, Windows 10 and Windows 11. This problem only happens in Excel for Microsoft 365. I didn't see this on Office 2016 or previous.
To help find the bug faster, This is how I recommend your developers test this,
Switch "Page Layout" mode, add text to the header, and add text to the cells from A1 down to at I94. Next scroll down to the bottom of the document then scroll back up. When the scroll bar reachs the top and you can't see the header text anymore then you know the bug is active.