TM FN 5-7 problems

[The Joker]

Every other shot just falls out the barrel :-(

I have a 2nd 5-7 and have been swapping parts about, think it might be the loading nozzle or hop unit, but can't find replacement parts anywhere to try it.

has anyone had similar problems? Or know where to get parts? Or are any other parts compatible?

Any help is very much appreciated guys