Originally Posted by DVE
Ok, thanks, I'll check results again.
Is it critical to freeze board to -18, if I'm not planning to fly at this temperatures? -10..+20 range for me may be enough.
If your card is very thin (<0,7mm) it can have problems making contact properly when inserted. If you put a piece of tape on the logo-side to make it 0.75-0.8mm thick, it will sit better in the slot and make better contact.
Sadly there is a lot of difference between the thickness of cards from different manufactorers. I have seen from 0.65 to 0.82 mm thickness.
There is also a small feathering spring on the slot itself that can be bent down to make the card make better contact:
(scroll down, first note)
SD card specification states operating temp from -25C to 80C