When bulk rail loaders or unloaders are part of a blueprint and wired up, the circuit wires are often (but not always) missing in the end. Happens with vanilla factorio + only this mod. It is not perfectly deterministic, but usually the same wires are missing. Seems to have increased in severity in recent factorio versions (0.18.3x). This of course means one has to manually fix up train stations.

Can you post a save / blueprint I can use to reproduce?

Thanks for looking into this - I don't think it has anything to do with the blueprint, the blueprint clearly contains the circuit connections. Anyhow, I made the simple blueprint below - it's basically two BRLs and two chests. When built by bots, the circuit wire between the two passive provider chests is always built, the other three are randomly missing (and very rarely, all are built). Screenshot at http://data.plan9.de/brl.jpg

0eNqllG2LgzAMgP9LPtdx9fXmXxnjqBpcQKu0nUyk//1ax8Q7HLjti5CSPHlSjRMUzRV7RdJAPgGVndSQnybQVEvR+DMz9gg5kMEWGEjR+kgJappOVKjAMiBZ4Q1ybtmuwlVJaM8MUBoyhPfGczD+yGtbOHjOl8qmq0kbKoPygtoEvdCaBgx61Q3kPRj0nXacTvrmjh2kaXxIGIyOEn4dD4lr6+aTWPok7bO4fyis1p2p8lrsTxzZs7Wrs4dd+JFdttjx6BU7vtMu2nhdQd+IEluX6d1u46YYf2h5qYrU3Wke903F/xcae2UGRtQzphBeN+RbU8RvTpHEH08R7bdMFkttnGd9McH8qW+JZc/ENrjpC1z+Ajfbz42PT7lueef1zle/EQYDKj0nZFnkNi8Ks/Tb2l+OcneE

I'm having the same issue as well. Only seems to have happened with a recent update. Either 0.18.37 or 38 or 39 is when the issue started for me. Prior to that all connections were reliably connecting.

Also, doesn't matter if copy/paste is used or create a blueprint.

It looks like significant part of the blueprint system changed in 0.37 when the blueprint book rewrite went in. In particular, positions are in world coordinates from when the blueprint was created, not aligned to a standardized blueprint grid, and blueprints are not snapped to the grid in any way when placed. This may take a while.

Oh yes, and the new "Grid size" settings aren't accessible at all, so as far as I can tell there's no way as a modder I can figure out where your blueprints are actually getting built, since they may snap to a completely arbitrary location. Unfortunately I don't see any way to fix this as of right now.

Maybe ask the factorio devs to make the settings accessible? They are normally very open to needs of modders.

Or maybe look at other mods that have extra items, such as LTN, whose train stop consists of three seperately placed items. Iff that has anything to do with it, of course - but LTN train stops safely connect.