DA Problem

I agree with above about the reed valves. Sometimes they get a little dirt or carbon under them. They can also crack or just warp. If they are not cracked you can usually flip em over and get some more use out of them. If parts are available still the stuff to do the valves are usually inexpensive.
However, if you have problems with the valves the symptoms are usually long run time. It takes much longer to build pressure because so much is leaking by. Does yours seem to be running longer than it used to?