I’ve had my ES 500’s for about 6 months now. Both failed (dead mics) at about 3 months and were replaced (with used units). Now the right one has failed again - same problem= dead microphone or Amp. (The chimes and bluetooth phone and music connections are heard well in both ears.) Still waitng after 2 days for Jabra response.
I read that others are having the problem too.
I believe Resound got a bad batch of michrophones … I have had 4 aids replace because of that problem … I am waiting for two Jabras to come back from Costco at this time.
The second set of Nexia’s seem to be working fine at the moment … fingers crossed 
I am still waiting to see how Jabra reponds. Bad electret mikes can happen. Bad customer service cannot.
P.S. I’m an EE and use electret mikes frquently. They are no longer rocket science.