Factorio Forums

To reproduce:

1. Click on a train when out of reach.
2. Switch to the fuel tab. (When was the ability to do this from out of reach added? I can't find it in recent changelogs. Is it intentional?)
3. Attempt to shift-click (or ctrl-click) fuel from your inventory to the train. It doesn't work.

However, these similar operations all work:

• Shift-clicking fuel from the train to your inventory, even when out of reach.
• Manually moving fuel into the train (by clicking on the fuel and then on the fuel slots), even when out of reach.
• Shift-clicking fuel from your inventory to the train when in reach.
• Opening the train from out of reach, walking within reach of the train with the inventory open, and then shift-clicking fuel in.

Honestly, I'm surprised you can even open the fuel GUI from a distance--I recall that wasn't allowed not too long ago, and I can't find any reference to a change, so maybe that's the real bug.

The bug here is that the fuel GUI is accessible at all when out of reach, which is covered by this post.