Weird horizontal Finder window scrolling issue since last security update

[AVR2]

Since the most recent Catalina security update, when you mouse over a Finder window, my 2012 Mac mini will scroll the contents of the windows slowly to the right. The only way to stop it is to manually widen the window to the point where everything is displayed anyway so there's no need to scroll.

At the same time, it's become almost impossible to listen anything in Music, because of an issue that sounds like the audio is being scrubbed by the mouse being slowly dragged to the right. The music files are all fine when played outside of the Music app.

I use a Bluetooth mouse, so I tried using a USB one instead and it does the same thing.

 

[Alchymister]

this scrolling problem - (only in horizontal direction, vertically it scrolls smoothly) - same issue on Mac OS Monterey.

 

[AVR2]

this scrolling problem - (only in horizontal direction, vertically it scrolls smoothly) - same issue on Mac OS Monterey.

It's not the smoothness (or otherwise) that bothers me, it's the fact that it's doing it by itself whenever the mouse pointer is anywhere over a scrollable window.