VGA asked me to look into the bug on Eternity E2M4 from this post
. Here's what's going on.
The exit sign sector is tagged with the same tag as the surrounding doors, activated by the lion face switch. I think this is a mistake in the wad, since there should be no reason for it. In either vanilla Doom or 3DGE, if you press the switch, that sector attempts to lower instantly, since its target of "lowest ceiling height" is opposite of the direction the sector is supposed to move due to the sector behind it being a closed door. (Same principle as instant-rising floors.) In either port again, if you press the switch from far enough away so that you're not under the exit sign, this instant-lowering happens and you are stuck.
In vanilla, if you are under the exit sign when you press the switch, the sector ceiling can't move to where it wants and so just gives up and does nothing I guess. However in 3DGE the sector waits for the player to get out of the way, before lowering to where it wants to go.
Further reducing the possibility of triggering this bug in vanilla is that the opposite linedef of the exit sign sector is a W1 trigger for the door behind you. In vanilla, attempting to use the switch before this walkover linedef is triggered won't work; the W1 linedef will eat the use action instead. To lock yourself out, you have to walk up to the switch, then back away, then press use. 3DGE is fine with activating linedefs through other linedefs it seems.
So this is kind of an 3DGE bug, but one that shouldn't make any difference on wads that don't also have a similar bug.