You must use a very good quality high class card .The best way to see if this is your problem , is drop the recording video size down to 720p ,if it keeps recording at the lower size the card is not good enough to go higher .
You must use a very good quality high class card .The best way to see if this is your problem , is drop the recording video size down to 720p ,if it keeps recording at the lower size the card is not good enough to go higher .