I have a standard cold machine that I installed about a year ago. Recently, the compressor has started to "clatter" a bit when running normally otherwise. It is especially noticable at night when everything else is quiet. Is the compressor a reed valve machine? That is the sound I'm hearing. I am a bit familiar with compressors and systems in general as I make my living designing LARGE industrial refrigeration equipment and have been for 37 yrs. This clatter is starting to get annoying. Have I got a compressor problem?