Hi,
Before anything: what Camera and memory card (brand and exact model) are you using?
Different cards achieve different writing Speeds even if they state to be same class and have max. writing speed of 30 MB/s (that's only a peak, in best case, not sustained at all).
Did you see a buffer overflow / filling icon appearing on the screen when camera stopped recording?
What you describe (if the card was low-level formatted and keeps with sane problem) seems to be: either the card is not fast enough or it is deffective.
.As an additional test you can use a card reader connected to a Computer to fill the card with files and check the transfer speed, and if it does it completely right.
If possible test the Camera using different brand 32GB card. SanDisk and Lexar are excellent (but of course they also have different models with different speeds)
Regards
