^, ^^, ^^^:
When my first M10 needed service, I was instructed to send it to the Teaneck, NJ service center. I'm on the east coast, so it may be based on your region. My internal mics had about a 3dB imbalance, and they promptly determined it was a manufacturing defect and sent out a new unit.
The microSD slot is a weak point. I used only the internal memory for a long time, but the first time I tried to use a card, I kept trying to put it in backwards. It's also easy to put it in the correct way, but slightly misaligned. You have to be very careful with it.
Because of this, I never take the card out and transfer through the recorder. The slow transfer speed is worth it to not have to deal with the card.