Whole chunks of the map missing on load

Describe the Bug

Just loaded a map i was working on yesterday to find out two whole chunks are missing. In the image below you can clearly see which ones are missing, the building is supposed to be symmetrical along the center.

To Reproduce

1. Save a map

2. Loaded next day to find parts missing

Screenshots/Videos/Twitch Clips

Additional Context
In fact is the second time this has happened, the first time was a few months and updates ago but the damage was minimun so I didn't think to much about it, being an early access and all. This time, however, I have lost a few hours of planning and building and was a little devastated to find it all lost. There's no need to recover the parts lost if it can be done at all, I need to finish it ASAP for a game tomorrow and will rebuild it as soon as I hit submit on this post. Just please try to resolve it so it can't happen to anyone anymore :)

PS: If the dragon head was damaged at all it would have been absolutely devastating as there are not yet (I hope) symmetry options for copy/paste and was painstaking to make.

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