Occasionally at random times my user interface keeps changing size. The content inside the User Interface will be magnified, and as such will not display the full contents of the UI for use of the program. The only way I can return the UI to default is to reboot the computer.
What is your desktop size?
Example: 1920 x 1080 pixels?
What hardware? PC? Tablet? Notebook? IOS or Android phone?
Just a guess, but look at his screenshot size (1920x1080) 
You’re right.
Was thinking of issues you had at one time with a tablet.
WOW that was a very long time ago.
With a windows 7 (Starter) OS, Acer Aspire One D255 laptop with only a 10.1" screen.
My desktop size is 1920 x 1080, and I am using a Desktop Computer with Windows 11 Installed.
Suggest performing a Repair of Avast One, always followed by a restart or reboot of system.
I have already preformed a repair from within the UI there was no change at all. However, as I have already said, if I reboot my computer without doing anything, the problem disappears for a while.
Yes I have this problem. Screen resolution is at 1920x1080. Deeply annoying as random, sudden huge increase in size of display inside the Avast One UI makes it unusable. Problem also goes away for a while after restart.