Browser alerts are triggering weird window resizing glitch

I am sorry but I am unable to recreate scenarios that trigger the alert popup in the guest profile.

I can’t access brave://apps and I can’t create bookmarks while in a guest session (the glitch also occurs when changing the location for a bookmark like mentioned in this thread).
I had the glitch occur when I tried to close my Gmail tab and it shows the “Are you sure you want to leave this site?” alert. But somehow I am unable to get Gmail to do it now.

I also stand corrected -
Based on the above-stated scenarios and some others I can’t remember, I was led to believe all alerts from websites trigger this glitch. But I tried using the alert from the W3Schools JS alert guide here and the popup there did not trigger the glitch in my own profile or the guest profile. (Odd!)

So, it is not all alert popups that cause this glitch.

Anyhow, sorry I couldn’t be of more help.
It would be great if you could help me find a scenario where I can have the webpage create an alert so I can test it both on regular browsing and in guest sessions and report back here.