I made a UEFN map yesterday and published it, no problem. I went into the Unreal Editor today, however, and it was gone, wiped clean like I had never even started. What happened was that I copied over one of my UEFN projects into this one when I was building it and set it to the priority, and did all of my stuff, but when I went back into it today the other map saved into that one was gone.
World Partition may be the culprit here.
I remember something similar happening, like I add a mesh to the level and then it’s gone, or I delete an actor but next thing I know it’s back on the level.
Turned out it was happening because of world partition that’s, AFAIC, is now turned on by default, and it keeps messing with the levels if you don’t use it right.