i struggled with this same problem for what seemed like an eternity - Chewaca, you know the thread i started:
https://www.sas1946.com/main/index.php/topic,33602.0.htmlit was a real nightmare to solve, and eventually it seems like it wasn't any one particular mod, but rather certain mods in a particular order.
i solved it eventually by removing the Engines Mod 2.6 and this visual mod (i also had the stand-alone turret fix mod installed, which caused me a problem, but probably you don't have that one)
after removing all the above-mentioned mods, i restarted the game and it worked.
don't forget to delete the 'last.quick' file in your Quicks folder!
anyway, removed them all, got the game running, and it's been perfectly stable ever since.
try in this order - if you use the FixFM part, it
must load before the Engines mod, and the main Visual mod folder
must load after the Engines mod.
this order is working fine for me.
if the Visual mod loads before Engine mod - null errors/30% loading crash
it seems there is some sort of inter-dependency between these mods, and they have to be loaded in a particular sequence to avoid these issues.
my current loading order is as follows:
!##00_PAL-VisualMODFixFM-v4111new
!SAS_Engine_Mod_4111m_v26
##00_PAL-VisualMOD-v4111new
for me, this solved all my problems. hope it helps.