I very recently experienced an annoying intermittent muting problem with a Japanese preamp purchased through this site. Had a high end salesman friend check it out and no, it was not my clumsiness with the volume/mute control. Contacted the dealer/seller within 3 weeks of receiving the unit (who indicated he had not checked the unit out as it came from a "trusted" consignee) and he directed me to repair services with advice that repairs were on him.
Needless to say after lengthy testing & analysis, various attempts to import non existent parts from The Land of the Rising Sun, multiple phone calls and emails to importer, repair station, seller, etc, etc, etc, the seller, a really treacherous swine, offers to trade in the damaged unit on a $20K amplifier, but he'll let me kiss his behind for the $300 repair. Both Audiogon & Paypal say they can't help as "time has run".
My advice: get EVERYTHING in writing. Verbal promises are factually worthless. Return any defective item immediately regardless of seller's promises. Now I've got to sue this !!*&%!!@ dealer in Small Claims Court... and that's going to be a real pleasure.