Molten tin for bobs/angels is not working.

I have the same issue.
A truck is sent, and will go back and forth but no liquid is loaded.

It also seem to apply to molten aluminium (but copper and iron and some others seem to work fine).

Yap, same here, looks like it is taking 0(zero) and sending 0(zero), they just keep going without doing anything (probably some kind of low payment protest or something similar hahahhaa). It works with other moded liquids like Molten Iron. I have posted it on the angels forms but they probably have tons of things already.
Mine was kind of small base so I just moved the tin next to the induction furnaces and used a pipe.
If it was some how a large base, I would have considered a barreling or canning of it.

can you provide a save game showing the issue?

Sure. I did delete my old map but it's easy enough to reproduce with creative mod: https://drive.google.com/file/d/1h_16X1-ihRB3rcsIRiIa_i-AFJjcWuvJ/view?usp=sharing

Just chiming in that I'm having the same issue with tin specifically. I tried it with copper and that works

I've done some testing in creative mode, trying all of Angel's molten metals. Molten aluminium, silver, and tin have the same problem. All the other molten metal fluids seem to work fine.

(I'd be happy to provide an example save-game file, but I'm not sure of the preferred procedure for that...)

P.S. Thanks for the wonderful mod.

Its should be fixed by the latest factorio update, it was a base game API bug