(Original author here) - here was a really hard-to-find bug - in some instances more than one quantity of fish could be placed in the same location - that meant the game would work fine until someone fished that same fish the second time and the fishing boats would diverge in the different simulations. The world sync check only counted the tile contents so we didn't see it. - There were actually two RNG's in the game, one was synchronized with the same start seed on all machines (basically the same random pool) for combat and whatnot - the other was unsynchronized and used for animation variance, etc -things that weren't gameplay related. Not knowing when to use one of these specifically (e.g. animals facing seems like animation but definitely affected gameplay if they could be hunted) could alter the code path and cause an out-of-sync condition.