I've been tracking this one down for a few days. Ever since I updated to macOS 13.3, window dragging sometimes looks like this.

It happens with any window in any app. It stops when I hide some(?) other windows. Not sure why and which windows, but I'm working on it…

Here's a better screen recording of the laggy-window-dragging bug I described earlier (currently filed with Apple as FB12122106)

https://youtu.be/h0bKmcsMFvw

FB12122106 Demonstration

YouTube
@siracusa that jittering tells me some other process is trying to update the window position as you're dragging it
@stroughtonsmith I’ve been assuming it’s the snap-to-window-edge feature that was added to macOS several years ago, but somehow going haywire since 13.3 was released.
@siracusa I would be very surprised if it’s not at all related to third party software. It looks like something is looping over your window list and reading/setting frames 👀 I can open a hundred TextEdit windows here without seeing any slowdown to snap, and I'm just on a Mac mini
@stroughtonsmith but is it an _Intel_ Mac Mini?