Not quite sure how to best go about explaining this, but it's not so much a bug as an overlooked change from the new map view adaptations.
When you click on a train that's nearby, so that the fuel tab is accessible, you can look into it. But if that train drives away you can still view the train on the map view, you can see the schedule, but you can no longer access the fuel tab because the train is too far away. (Which is how things used to work just fine.)
Now if you exit the train view, but reselect the same (now distant) train from the map view, you are able to view the fuel tab regardless of distance. This post is to perhaps suggest changing the mechanic to allow access to the fuel tab from both menus?
Hopefully the video below can describe the situation better:
