I've been shooting video with no problems using a SanDisk Ultra Plus 16GB 80MB/s SD card and recently picked up a second one. The exact same card.
On the first one, I can shoot as long as I need. The new one I bought stops after 5-10 seconds. I tried formatting it in the camera and on my PC without any luck. I also bought a few Lexar Professional 32GB 95 MB/s cards and they stop after a couple seconds as well, even after being formatted.
Any other suggestions for things I can try? I'd really prefer not to have to return these and buy CF cards but I'm losing hope and have an event next weekend....
I would suspect a counterfeit SD card if it is not performing up to spec. Lots of counterfeit cards out there.
I suspected an off brand card. Have not ruled out a counterfeit card, either.