So I tried to load my current map I use on my server(ver 1.12.2) into 1.13 pre6(and 7) and the land on the right half of my spawn area was basically regenerated with a ravine and more than half my buildings are missing. For those of us that run public servers, do we HAVE to reset all maps and start from scratch? Does 1.13 use a different world generation algorithm than 1.12 because of the new biomes? I even tried just using the same seed to generate a new 1.13 map and that same ravine appears at my spawn coordinates. Also note that the water/ocean area from the complete spawn is completely missing from the one that is cut in half. Please see attached pictures for visual reference.

EDIT: 1.13 pre6 had the ravine...  in 1.13 pre7, the ravine is gone, but so is half of my spawn still...