Artillery wagons won't load shells

[samuri]

I've been messing with this for ages, can't find a fix. I have a train which stops at every stop, held on inactivity. The cargo wagons are completely full. I have two artillery wagons at the back which won't load shells. They will load manually fine and once loaded will fire as expected. They won't load automatically to any point in the wagon. I've tried different loaders, have defined shells specifically in the loader filters. No idea. In the screenshot the front wagon shows it has shells because I put them there manually, the rear wagon currently has no loader. They flash no ammo when empty.

[boskid]

Not a bug. Those inserters are too far from the rails. Move them down by 1 tile.

[samuri]

Oh my god, so obvious. Thanks.