I started a new MP game for me and a friend on 13.11. I played about an hour, and when he came on he was stuck in a desync loop. I logged off and tried to reconnect and was stuck in the same loop. We started a new map on 13.11, were both able to get on, played for about 3 hours, and when I tried to reconnect today I was stuck in a desync loop again. I updated client and server to 13.13, and have the same problem. The save file works just fine locally.Edit: I resolved this removing the Bottleneck mod. I'll leave it here for anyone else who runs into this. I opened the game locally, used F5 to see what script was using the most time to process, and it was Bottleneck. I updated to the latest version from github, and it's still a very slow script so I've removed it altogether until it's fixed a bit.
For clarification, what I'm calling a "desync loop" goes like this: connect to server, download map, world loads up, 2-3 seconds later the desync message pops up and the map redownloads, and repeat. I'm not in the game long enough to actually quit, and the only way to get out of the loop is stop the server or quit the client itself.
I assume it's related to a modded item in the world, and I'll continue removing mods and restarting after I finish this post (and update if/when I discover the issue), but hopefully this bug report will help track down this edge case.
Mods folder can be downloaded here: http://www.sickhippie.com/mods.zip
Let me know if you need anything else, I'll be happy to run any tests you'd like.