Well I think the problem is with deadlock and compatibility with Advanced Belts.... (I guess it could be Maraxsis but I dont think that mod uses a loader), but here is the error.

Failed to load mods: Error while running setup for entity prototype "turbo-transport-belt-loader" (loader-1x1): next_upgrade target (extreme-belt-loader) must have the same collision mask.

deadlock-beltboxes-loader
maraxsis
AdvancedBeltsSA

(Disabling Deadlocks makes the issue go away)

huh?
My guess is Maraxis changes collision due to how that planet works.

I tested the update thoroughly and it was working just fine. The screenshot I added to this mod shows the research that adds the elite tier of all the things, including deadlocks stuff. So I know it works.

I encountered the same situation as the OP

All I do is call the same make_tier() as the base deadlock mod adds and uses. And I know it works as I was able to load it just fine.

Some other mod is over-riding the collision mask of the turbo loader by deadlock. And doing it in a way that doesn't take into account other mods.

i filled out a bug report on Maraxsis github