just a few minutes ago I loaded up my build team's (astrington) map we have been building over the course of that past few months in a single player copy to take some screenshots of a few of the areas, I got done with takeing some around our capital city that is at spawn and started heading to one of the other towns to get some there. I got about halfway there to find that almost all of the northern chunks of our custom terrain world had been overwritten with default chunks. I then thought that perhaps it was just something that had recently happened with just the single player copy and it was not like this on the realm that we use to build together. so I loaded up the realm and went to the area I had found it at to make sure that the current copy was ok, but it also had the chunks fully overwritten. I am not aware of when exactly this happened but It must have been within the last month because I had visited the affected areas within that time, I also had entered the areas in 1.14.4 so I know it is not a bug with updating to a new version because it happened after it was changed to 1.14.4 from 1.14.3 and it has not been played in any other version since. we lost several months of progress from this bug and I don't think theres any way to un-do what happened on our end because theres no telling how long it has been like that but I wanted to make the developers aware of the bug so it can be fixed and no one else goes through such a crushing lose of progress and work.