I have the same problem, but it's unrelated to the experimental release. I'm not convinced that the problem is tied to FPS, but I do see the FPS drop quickly into the red zone when the lag occurs.
The problem is only noticeable when using a vehicle or the jetpack. It may exist while walking, but I don't see it.
The problem gets worse the more the map is built out.
I cannot find a correlation between CPU / network performance and this issue.