Bluetooth HC-05 module failures

[Wimberleytech]

I have purchased four HC-05s on Ebay.  A pair worked fine initially but then one failed (no LED heartbeat).  I substituted one of the others I had purchased.  Worked for a bit (off and on over a period of days), then failed.

These are connected to Arduino nano pro 5V boards.  I have properly handled the 3.3V RX input coming from nano 5V TX output, so that is not the culprit.

I checked the 3.3V regulator on the dead boards, and they are functioning properly.

Anyone else experience high failure rate with these ubiquitous HC-05 modules?