Pre/PostDrawViewModel gamemode/swep hook not being called.

I have a SWEP (it’s pretty lengthy) but sometimes in TTT the weapon nor the gamemode will called Post/PreDrawViewModel and I can’t figure out under which circumstances this happens. It also only happens to some players with the same weapon.
Does anyone know what will cause the view model to never render at all when the SWEP is active and SWEP:Think() is running?