Jerry,
You could not possibly be any more wrong on the Junior. Hands down it is the best unit of it's size for filling individual scuba cylinders. You bought it after someone rebuilt it. Don't you see a problem there? Who rebuilt it? Your 'compressor guy' is likely a low pressure compressor mechanic and I highly doubt an authorized Bauer distributor. If Pablo down the street rebuilt the engine in my Toyota and it crapped out on me I wouldn't be blaming Toyota.
You are right, Bauer parts are not cheap, but they are good. Pay for quality or don't, it's up to you. You want the job done right, go to a factory authorized distributor that will use authentic Bauer parts and you can easily get 1,000 hours on the unit before needing to start replacing valves, pistons, rings, etc. Have Pablo rebuild it and you are in the position that you are in.