i would hazard a guess and say the bottle might not be screwed in properly, right pain with pmr's. Sounds daft but check the battery as well, they are crap with a low batt in.
Other than that reg could need cleaning or the orings inside, if there is too much grease on the orings it wont like it too much. Use dow 33 as well but you probably know that anyway.
Cant think of anything else off the top of my head
though report back when you get more air etc and we can all put our thinking caps back on if needed.
Jon