One R dropped frames

I've just started using the One R with the 360 mod and every few clips I'll start shooting then it will be unresponsive to stopping. Then I either have to leave it for ages or hit the power button which gives me a 'dropped frames' message and the video ends up being a second or less of footage.

is this a know issue? does it have something to do with the sd card I'm using which are supposed to be within the requireedlyrequireedlyrequired