Alright, maybe I pushed it too much, but I had to try to complete a custom quest on the latest build. Unfortunately, I forgot to save after getting the Boss Key, and that...cost me. After going through one or two phases of the final boss, it crashed on me. The files are attached below, split into two parts.
I may try to beat the quest again in a few days...maybe even after I wake up. I know I'm capable of it. Hopefully 1270 is capable of it.
Hm... this isn't good news. I'd bet that it crashed due to a wave-effect warp, which it would sometimes do in version 2.10 in windowed mode. It never crashed, however, in fullscreen mode, which is a bit odd. This glitch might be back in 2.5. Can I ask, (1) are you using ZC in fullscreen or windowed mode, and (2) do you remember what happened right before it crashed?
I was in Windowed mode. Full screen looks terrible on my end. Before it crashed...I just finished off the second wave of enemies the final boss summoned.