Using the 0.8.10 binary release and my own compile of the commit aa8020881b11683050b3e869d387186a24c7ed53 , Fastdoom consistently desyncs when trying to play back demo3 of Plutonia with no sound or with sound and no music, causing the player to fail to kill the third imp, but will consistently crash when music is enabled regardless of whether sound is enabled. The 0.8.10 binary release crashes immediately with music, but my compile of aa8020881b11683050b3e869d387186a24c7ed53 using the latest NASM, DOS32/A and Open Watcom C 2.0 2022-03-12 Build will crash within a few seconds of starting the demo. This happens on DOSBox and on real hardware - tested on a 386DX-40 with an ISA Cirrus Logic GD-5429 and a Creative Sound Blaster 16 CT2290 and Ensoniq Soundscape S-2000, but this is 100% consistent so I don't believe that the hardware configuration matters.
This happens with both the Steam and GOG releases of Final Doom, which use slightly different IWADs (the GOG release is also known as the id Anthology version - https://doomwiki.org/wiki/Versions_of_Doom_and_Doom_II) but it does not affect the outcome of demo3.
Further investigating by warping to the map shows that it's not an issue with demo3 in Plutonia, but that the map itself crashes. I've updated the bug title accordingly.
Using the 0.8.10 binary release and my own compile of the commit aa8020881b11683050b3e869d387186a24c7ed53 , Fastdoom consistently desyncs when trying to play back demo3 of Plutonia with no sound or with sound and no music, causing the player to fail to kill the third imp, but will consistently crash when music is enabled regardless of whether sound is enabled. The 0.8.10 binary release crashes immediately with music, but my compile of aa8020881b11683050b3e869d387186a24c7ed53 using the latest NASM, DOS32/A and Open Watcom C 2.0 2022-03-12 Build will crash within a few seconds of starting the demo. This happens on DOSBox and on real hardware - tested on a 386DX-40 with an ISA Cirrus Logic GD-5429 and a Creative Sound Blaster 16 CT2290 and Ensoniq Soundscape S-2000, but this is 100% consistent so I don't believe that the hardware configuration matters.
This happens with both the Steam and GOG releases of Final Doom, which use slightly different IWADs (the GOG release is also known as the id Anthology version - https://doomwiki.org/wiki/Versions_of_Doom_and_Doom_II) but it does not affect the outcome of demo3.