I'd been playing this WAD for a bit and had saved a number of times, and died a few times and reloaded too, when, on getting killed by a Spectre, I got a crash. I restarted GZdoom and tried to load my save game and immediately the game crashed again. So, my guess it's a corrupted savegame problem of some sort. I've attached a crash log and the save game. In case it's relevant, my saving had been done by hitting F6 (quicksave).
Here's what I get from a debug build when trying to load the attached save.
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