If it is any similar to the gas stoves in my kitchen it is either a problem with the nozzle (I don’t know how it is called in English, the thing with a tiny hole where the gas comes from) or that the air intakes are dirty. Sometimes the air intakes aren’t obvious at all so my recommendation is to clean it all as thoroughly as possible.

Yellow isnt hot enough.

Sometimes that’s because of grease and shit that’s burning less efficiently, and you just need to let it run and it’ll fix itself.

It doesn’t look like that though, so maybe carbon is built up?

So you can try to clean it, use a toothpick.or something to make sure there’s nothing clogged.

There’s a chance the fuel is just old, but I’d imagine you checked that first and probably even a new container, but worth mentioning in case you haven’t.

A proper cleaning should do it. Make sure all the air holes are clean.

Big yellow flame probably indicates its not getting enough air mixing with the fuel for complete combustion. I’m guessing something got clogged up with soot, or possibly rust. Look around at all the little holes the gas comes out of, see if any of them are clogged up. If you find some, something like a safety pin can probably get them opened up.

Impure butane can cause this. Reseat the canister to make sure it is sealed correctly. Check the o-ring. If all of that’s fine and it still happens, switch cans and try again.

Yellow flames usually mean either sodium salts or hot soot particles. The shooting bit makes me pretty sure it’s clogged with one of those two, although it could be a sudden burnoff situation more than actual pressurised shooting, without seeing it myself.

Others have suggested possible root causes; I have less experience with this particular thing than combustion in general. Taking it apart, if possible, should give more information. If not, you have to figure out how to wash it inside, or change combustion conditions to increase air relative to fuel and burn off any built up soot.