During my trip to North, my M11 acted strange thrice.
First, it just plain froze. Nothing happened on shutter release. No button activated the rear screen. Turning the camera off didn't close the shutter but left the sensor visible (lens still attached). I had to remove the battery and sweat for 10-15 seconds before re-attaching the battery and doing couple power cycles. Phew! Worked normally for the rest of the trip.
Second, few days later I got an SD card error. Fortunately I had couple of cards with me. I lost a few frames there, because it wasn't recording them to the internal memory neither. All the previous frames from the memory card were accessible both in-camera playback and also on computer. I have now formatted the card by re-writing the whole card and I will try how it will work. It is rather expensive Lexar card, which is recommended to be used with Leica.
And third, using Kingston SD card, the camera stated the card was full, and I just thought well okay, maybe I have already shot that many frames and changed to another card. When getting home, the card had still like 14GB (64GB card) left..?
These were first time ever I was having any kind of issues with any kind of memory cards with cameras. I have used multiple brands of multiple capacity CF and SD(XC) cards during the years on multiple camera bodies.
Should I be worried? The cards I've been using are relatively new, not like some 10 years old, multiple times re-written and formatted ones. Although very rare, the freezing issue still seems to be present. That part I'm not worried about. Is it possible to somehow clean the cameras SD card slot contacts?