No, it's not an insider build. It was an automatic update via windows update that happened last week... But before that, with 21H2, I had this problem also.
I've tried to enable and disable many of the visual effects of win11, but none of them have any impact on this problem
Maybe you can reproduce this problem by doing the following: open any folder, then minimize it, then alternate between desktops... This pattern makes the problem appear here 100% of the time! I have to CLICK somewhere after minimizing a folder (or a browser, or anything), otherwise the taskbar problem happens.