Noticed in your ep 2 of making the Titfield thunderbolt on a budget your using humbrol plastic cement without the needle. I'm guessing the needle clogged up with glue. Tip for you. If you remove the needle from the glue tub, hold it with a pair of needle nose pliers or tweezers and use a lighter to burn off the glue inside the needle. You should see the glue popping out the end. Have some water on hand to cool the needle down. Then when you put it back it should work. Cracking work bud, keep it up