Put a wax capsule of water in the input slot --> goes into the processing slot --> water goes into the loco --> capsule still containing water goes in the output slot.

Did I mention I hate fluid containers?

I think this is forestry bug because they did not define their container item for water wax capsules correctly.

I need to check if I even fixed the GUI for the locomotive.

IC2's fluid/solid canning machine treats wax capsules properly.

I think the train treats buckets, ic2 universal fluid cells, and foundry capsules properly, right?

Does the train handle lossy containers properly? Ones that are destroyed upon use?

@CovertJaguar It has three slots. I know what is the fix already.

If the GUI only has two slots, then the Locomotive needs a GUI redesign to handle these properly. If it has three slots, then there is a bug in the container handling code.