Windows will shrink/reduce to nothing while using the Mission Control feature. This applies to both the button and the three finger gesture. No other workspaces are open, and I have attempted to both restart the system and the dock, to no success.
defaults read com.apple.dock only shows that
showMissionControlGestureEnabled is enabled.
Unfortunately, I lost track of when this first appeared. If someone could nudge me in the right direction to diagnose the issue, I could tinker.