30 units available 3 colors same function.  I have sold over 50 of these units. We bench test all units. Before i ship i would like to talk to buyer and discuss what is the problem with there unit.  I have had a couple returned claiming they are defective and when returned we retest and nothing wrong.  ebay frowns on defective items and lowers your seller rating.  so discussing problem before shipping will help with this issue.  Lastly we mark all parts.