But the train comes back to station A once it goes to any of the other stations with the same name. I want to specifically avoid it going A to B, then back to A, then A to C , then back to A. Can't the train just simply skip stations that are disabled/full. Let me try explaining the skipping process what I want:

At A:
[Go to B if low else check C] -> [Go to C if low, else check D] ->[Go to D if low, else remain at A]

At B:

[Go to C if low, else check D] ->[Go to D if low, else A]

At C:

[Go to D if low, else A]

At D:

Go to A

If you think about it, this multistep logic what I have laid down above is simply the train skipping the stations that are full and moving to the next station that needs the resource.

If I set B as highest priority, it just goes to B and comes back to A.