Hello! We've noticed that in DayZ Experimental 1.21, when riding as a passenger in a car, the motion is extremely choppy/blurry - almost as if something isn't being interpolated, properly. It is perfectly smooth for the driver, however. This issue doesn't exist in Stable 1.20.
Here is a video demonstrating the issue. It is from my perspective and it starts out with me driving. You'll see it is perfectly smooth for me, but my buddy in the passenger's seat says it's choppy for him. At :30, we switch seats and he drives, at which time it becomes perfectly smooth for him, and you'll see it is choppy for me.