Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Disappointing Hitachi quality

I bought a like-new Hitachi EC12 compressor from a fellow woodworker. I encountered the following problems.1. The pressure regulator leaks air. You can hear the air leak when the working pressure is set below 90psi. At higher working pressure, the leak is not as noticeable. It also seems that Hitachi uses non-standard thread as standard 1/4" hex nipple does not fit. I had to reuse the hex nipple came with the unit.2. The unit does not hold pressure. Over a 12-hour period, it lost about 20 psi of air. I have noticed the unit will refill the tank periodically even though it is not being used.3. The unit fails to run sporadically. The motor makes a humming sound but the compressor will not kick in. The motor will stop in a few seconds and the same cycle will repeat every few seconds. The only way to get the unit working again is to cycle the AUTO/STOP switch.I am really disappointed by the quality of this Hitachi air compressor.