Okay, I've got 4.3.3 compiled on my laptop which runs a distro based on 18.04 (though it seems unlikely OS has anything to do with this). I am still unable to reproduce this. The steps I followed were:
- Run with "gzdoom -config fresh.cfg -iwad doom2.wad -file friendly.pk3 -warp 2"
- Grab the CD straight ahead from the level start.
- Without bothering with the switch, slip through the gap into the hallway and go to the "house" area where the camera quest giver is.
- Talk to the camera quest giver, do the quest, turn it in.
- Fly in through the opening into the level's only secret room.
- Fly out and grab the red key.
- Fly back into the secret room and take the teleporter back to the level start.
- Slip through the other gap into the other hallway, and head to the sunken area with the barrels.
- Grab the blue key. Head through the two blue key doors into the exit room.
- Talk to the fishing quest giver in the exit room.
- Go right outside into the hallway and fish in the water there. Catch the fish.
- Turn in the fishing quest with the guy in the exit room.
- Press E to bring up the Inventory screen.
- Press Tab to bring up the automap.
- Press Tab to dismiss the automap.
- Press E to dismiss the Inventory screen. (Alternately tried clicking the checkmark button to close the Inventory screen, same result.)
Do these steps reproduce the issue for you?
If you're comfortable capturing some video of a session, that might be useful.
Thanks for the info, sorry this is a weird one.