As suggested by a user in a Reddit comment on my post entitled “Glitches when maximising and restoring windows” within the /r/KDE sub-reddit:
it’s a bug that’s caused by the panel trying to get into the maximized view (non floating mode) while another windows is alredy maximized, any change to this fixes the animation glitch, you can set the panel to autohide/dodge or set it to non float by default.
So, I disabled the floating panel and so far haven’t seen the issue. Fingers are crossed.