Well I am trying to work on higher bitrates from the 1080i and the 720p settings, but its proving very difficult. About the card, yeah, as Ralph_B said the extreme pro has a lower write speed (as do any of the UHS-I cards it seems) but I've not had problems. Although the only one I use is an 8GB card, I've seen people post on here with larger extreme pro cards that have definitely had speed write problems, and those that haven't. Its all pretty vague.

Just did a quick test shooting detail and moving the camera about a fair bit in ETC mode. I got the same message you did trying to playback in camera. Another shot without ETC recorded after it played back in camera fine. I didn't create anything that looks as dramatically bad as you managed (as I really, really moved the camera about so it's hard to tell through the blur) but there are definite dropouts looking at it in streamparser (as in B frames of only a 7,680 byte size). Static shots seem okay with ETC though. So yeah, its not stable with the ETC mode, nice catch, thanks for the info. Dunno what to do about it however.