I'm having constant desyncs as well. Playing for 1-2 hours on the map. Both players getting desync if the other one is host.
Using 0.13.3 without any mods, Windows 10.

I think the last thing I crafted before the desync was an offshore pump, maybe this helps!
That's a different desync and resolved ...

I was able to reproduce the problem! Use this savegame: https://www.dropbox.com/s/rp8tdmqh46pjy84/broken_save.zip?dl=0
I used two factorio local instances, one steam and one drm free. Server host is "Mr. Turret", connect as "NT" with 2nd instance.

As Mr. Turret:
- Run down the 3 transport belts and ...

I'm having constant desyncs as well. Playing for 1-2 hours on the map. Both players getting desync if the other one is host.
Using 0.13.3 without any mods, Windows 10.

I think the last thing I crafted before the desync was an offshore pump, maybe this helps!

desync report: https://www.dropbox.com ...