This is a bizarre one and I want to make sure the problem is on my end rather than some subtle issue with GZDoom.
I'm sorry the steps to repro aren't simpler for this; I tried to create a one or two file small and simple test case, but couldn't because it involves IWAD content.
1. Use the latest version of WadSmoosh to create a doom_complete.pk3 with both Doom 2 and Final Doom content.
2. Launch GZDoom latest with this PK3 IWAD and from the console open PL_MAP30 (plutonia map30).
3. Proceed into the level and step through the first teleporter.
4. Observe: the line trigger you hit just before the teleporter did not fire as it does with Plutonia.wad, causing you to be sunk into a pit and unable to get up and proceed with the level. (without archvile-jumping, which isn't the intended progression obviously)
5. Exit and open the WadSmoosh IPK3 in SLADE. Open doom2.wad alongside it. Copy doom2's PNAMES and TEXTURE1 lump into the root of the WadSmoosh IPK3 and save it.
6. Relaunch with WadSmoosh and reopen PL_MAP30.
7. Proceed through the teleporter and observe: the line trigger works as expected this time.
8. Optional: Try the PNAMES+TEXTURE1-less IPK3 from steps 1-4 with GZDoom 3.6.0 or earlier - the issue doesn't seem to occur, because that version's texture handling code is completely different. (You may need to remove the ZScript file from the IPK3 to have it work with that version.)
Was this a GZDoom bug introduced in 3.7.0, or am I doing something wrong with WadSmoosh by not including a PNAMES + TEXTURE1 lump? I added the extraction of those a long time ago to fix some rare PWAD compat issues, but then recently removed that because I knew it wasn't necessary (100% of the actual textures WadSmoosh has are defined in a series of plaintext TEXTURES lumps). I'd prefer to not extract data unless I know exactly what it's doing. The bug report on my side is "Plutonia map30 doesn't work properly", but there's clearly something deeper at work.