Final Doom and Doom95 demos out of sync

I always thought that the Final Doom Doom2.exe and Doom95.exe had fixed the lost soul bug so both exe's would act the same but when I record something on the FD Doom2.exe it goes out of sync on Doom 95 and the same when recording with Doom95 it goes out of sync on the Final Doom dos exe. Can someone tell me why this is happening and please do tell me more about the two source ports.

Doom 95 is based on the Ultimate Doom engine. It is therefore incompatible with the Final Doom engine demos.

http://doomwiki.org/wiki/Versions_of_Doom_and_Doom_II
http://doomwiki.org/wiki/Final_Doom#Engine
http://doomwiki.org/wiki/The_Ultimate_Doom#Engine
http://doomwiki.org/wiki/Doom_95
http://doomwiki.org/wiki/PrBoom#Compatibility_modes_and_settings

Final Doom introduced a teleporter bug. A fair proportion of demos desync because of that if played back with the wrong exe. Maybe 15-20%? I'm not sure because I've never tested for that particular type of desync over a large number of demos.

By way of comparison, the two differences between Doom2.exe and Final Doom (lost soul behaviour and teleport bug) altogether lead to about 30-35% of demos desynching, with a higher proportion for longer demos, and lower for shorter ones. If there are no lost souls or teleporting, then there will be no desyncs. The presence of lost souls or teleporters does not guarantee a desync.