Sorry to hear you're having problems. Unfortunately I don't know what you mean by "my video is laggy/choppy". Do you mean when you press play on the camera? Or when you play it on a computer? Or in some kind of editing app? Also what does "laggy/choppy" mean? Any chance of a sample?
Generally I've found that 4k @ 59.94 works fine. But when you come to edit it, your editor may have trouble keeping up, and then you will get stuttering in the editing app. If that's so, then it's not the camera's fault. A more powerful computer, or a proxy workflow, might help. A video player on your computer can have problems too, if the computer isn't powerful enough.
If you post a sample -- like take a short clip from the camera, and post it on Dropbox or something -- then folks here can see if it's choppy for them, compared to what they normally shoot.
