Ok, couple of things:
First of all, your write speeds are ok, but not great, and that could be part of the problem. Hopefully all of these write speed issues will start going away as soon as those new 1200X cards come to market.
Secondly, it sounds like you're shooting in crop mode, I haven't had particularly good results in crop mode. If you're shooting at standard 1920X1080 resolution, you probably shouldn't shoot in crop.
IMHO crop mode isn't particularly stable and I have gotten weird frames myself. I don't use crop mode unless I'm doing very short and very specific shots where I really need that extra magnification.
First of all, your write speeds are ok, but not great, and that could be part of the problem. Hopefully all of these write speed issues will start going away as soon as those new 1200X cards come to market.
Secondly, it sounds like you're shooting in crop mode, I haven't had particularly good results in crop mode. If you're shooting at standard 1920X1080 resolution, you probably shouldn't shoot in crop.
IMHO crop mode isn't particularly stable and I have gotten weird frames myself. I don't use crop mode unless I'm doing very short and very specific shots where I really need that extra magnification.