[solved] UMAPINFO problem

[Laocoön]

I have been working on a wad that I would like to be compatible with multiple source ports, including GZDoom, but I am having some issues.

The intended map order is as follows:
Map29 --> Map33 (Final fight) - this works fine (MAP33 is the final fight so that monsters don't telefrag each other)
Map33 --> Map30 (normal exit). Map30 is a small map displaying the ruins where the boss used to be (squashed Romero). The normal exit here ends the game, with a message that you suspect this is not the true ending
Map33 --> Map34 (secret exit) Map34 is a secret map, which leads to Map35, which is the true final map of the wad.

For some reason, instead of sending the player to the intended maps, this happens instead:
Map33 --> Map30: return to title screen
Map33 --> Map34: correct message is displayed, and a tiled version of the correct pic, but then nothing: just a black screen instead of the intended map.

Now, here's where it gets increasingly complicated: the wad used to have both UMAPINFO and ZMAPINFO. The former plays well with DSDA-Doom etc., while the latter works with GZDoom, of course. Unfortunately, MAP35, is a secret map made by a guest mapper and it uses bossactions in UMAPINFO to make sectors lower, first when all the spider masterminds are killed, and then in a later fight when all the cyberdemons are dead. I couldn't figure out how to do this in ZMAPINFO and the mapper in question has gone off the radar lately due to work/life issues. So, I just deleted ZMAPINFO (I do have a backup), in the hopes that UMAPINFO could handle all this (I also hate working with clusters, and I hate always making sure that changes in one MAPINFO are also made in the other one so they are in sync). And it does work fine throughout the wad, except that for some reason it refuses to send the player to the correct maps towards the end of the wad.

I was adviced on the Doomworld forums to report this as a bug in GZDoom and to just release the wad since it works well in other sourceports, but I really want it to work in GZDoom, which is my port of choice. Is this a bug or does it have something to do with GZDoom not supporting recent revisions of UMAPINFO? Do I have to reintroduce my ZMAPINFO to the wad, and if so, how can I implement the bossaction stuff from map35?

I've included a link to the wad, but without map35 in it, since I don't have the author's permission to share it.

EDIT: link removed; issue solved. For some reason, "endgame = false" caused GZDoom to think there were no more maps after map 33. Dunno why.