This is for a friend of mine who is having this exact issue in-game. His whole process is as follow:

Made a few masks through OBJ => Model before, worked out by trial and error (2 years ago, used mod_override)
Made a SuperBLT type mod for the purpose of porting (for now) a magazine from modern Wolfenstein to the G3
Figured out the weaponfactory tweaks lua through examining other mods
Figured out main.xml, to load units / mod properties
Already familiar with .unit and .object and .material_config for previous purpose of porting assets PD2 => GZDoom / Fallout NV
Textures are in DXT5 DDS (properly renamed)
Model was imported through Payday2 Model Tool, from G3 default magasine to GLB, replaced with Wolf's magazine, exported out, made into .model as new object
Already was able to implement the new mag in the weapon modification menu.
Got localization working
Got menu icon working
Got got stats change working
Trying to preview the mod's assets ingame causes infinite loading loop (the three squares). No crash, just hangup on loop.
Game's log does not show any errors related to the mod I made.

Is there any way this issue can be fixed or worked around?