When crossing chunk borders near a chunk with complicated geometry, in my instance a chunk filled with oak_fence_gate, there is a minor lag spike. This is not MC-123584 as that pertains to updating chunk geometry, and in this case, the geometry need not be updated for the lag to occur. This is also not MC-162253 as this occurs when crossing any chunk borders near the afflicted chunk. attached is a screenshot in which the player is being moved back and forth across a chunk boundary by a piston, demonstrating the lag spike. Notably, this occurs regardless of method of transport, a piston is just a convenient way of demonstrating for a screenshot: