https://www.youtube.com/watch?v=RN3i_YWHYak

In the above video is a machine that does a relative teleport of the player every 100ms (2 ticks), alternating between 1,0,0 and -1,0,0. As can be seen, this is mostly seamless but occasionally snaps the player back quite a bit. Though it's not in the video, sometimes the player also gets "stuck" where they can't move or turn their head because they are getting snapped back constantly, much more rapidly than the teleports. I have slowed the machine down to one second between teleports and am still having this problem.

Note that this happens both in single player and on a multiplayer server running locally. The server is having no trouble keeping up with real time, and there is nothing in the console aside from the output from the command blocks.

UPDATE: I notice that if the player is crouched when they teleport, their view angles are reset to zero and they will uncrouch, 100% of the time. This may or may not be related.