I recently saw claims that the various loader mods tank UPS when heavily used with trains due to how the game handles items & trains (not a loader flaw just a limitation of how the game is built).

I figured I'd go to the source to see if true, especially with one of your recent patch notes talking about only performing train logic when actually using a train.

Yes, Loaders utterly tank ups when used with cargo wagons.
Base implementation of loaders only connects to chests and crafting machines. Cargo wagons are an addition written in lua.
Originally I didn't even want to include it for how badly it drops ups. But just like with snapping away from chests ppl cried so long until i added the blasted thing.

Well that is disappointing and probably explains why my last game declined so rapidly after I found loaders - I only really use them with trains. Looks like I'll have to revert back to double-sided load|unload with inserters for best throughput.

I appreciate your work and hopefully in the future the dev's will "correct" this flaw and I'll be able to use them en-mass again.