One of my junior alu cylinders has a sticky valve, which means when taken off the gun or the charging adaptor the valve does not automatically close, and hence dumps all of its air. It seems to be worse when there is less than 100 Bar in the tube so presumably the spring works better when there is some air assistance behind it. What are my options to fix this? Can I swap out the valve/tube end assembly with one from a spare standard steel cylinder? Clearly it needs a special tool to get the end off, I'd rather not do this myself so does anyone work on these? I guess there might be dirt in the valve; could this be cleaned or is it not accessible?