Train stopping at refueling station and not refueling

For a while now, my trains have been jamming up, because a single train stops at the refueling station, and just sits there. It says it's moving, if I slow down the game, it's flickering between moving and searching for a path, it appears to be fully in the refueling station, but instead of filling it, it will park, and sit, and jam up the entire network eventually. The save game is centered right on a train doing it at the moment of save. If I click and refill it with unity, everything goes back to running normally for about 15-20 minutes until randomly another train jams up the refueling station for apparently no reason.

At one point, they all parked at the waiting stations empty, and I had to refuel each one individually with unity. They have not done that since.

The engines are not using their coal tenders. I've seen several trains "out of fuel" while just the first engine is out of fuel, but the 2nd engine and the tender box are full.

This is getting really old, having to manually refuel my trains every 10 minutes : /

Engines only use a tender that is directly behind them. Each engine needs its own tender.

Good to know, thank you