Garmin 3790LMT speaker problem


I purchased my 3790LMT about a month ago and all was fine for the first couple of weeks... and then I plugged it into the mount one day, heard a slight (but constant) hum, and got garbled noise through the speaker (almost like the speaker had been under water). When I took it out of the mount, the humming noise stopped and the sound worked fine through the internal speaker. I plugged it back into the mount and immediately got the humming and garble again. I used it for about a week with garbled noise before I called Garmin and they shipped a replacement mount/speaker. Everything worked fine again.

Here's what's weird. I knew I hadn't damaged the original mount, so I put it back into my car and plugged the GPS into it. No humming, no garbled sound. I had checked cable connections before, so that wasn't the problem. Not sure why my speaker decided to behave again.

Has anybody else had speaker problems?