No mods were used. and I don't have to do anything specific to repro. I hit it just walking around. It might be specific to areas with lots of belts. I didn't see this as much earlier in the save.

Every 1-100 seconds. It's very reproducible and not very playable. Single user on headless 0.13.8 server. Solid <20 ms connection to healthy server. Been experiencing this since 0.13.6 (possibly on 0.13.4 as well). Desync report attached.