So sometimes I try to join beta for a day then come back, and for that I need to export my worlds so it won't be lost during the beta converting. The weird thing is that not all of the worlds gets exported correctly... Some of the worlds gets an error after I import it back. So I tried to investigate in this and went to the exporting files (which I called "All worlds backup to try beta"), and what I found wasn't expected. I found out that some of the worlds size is 0KB unlike the other worlds. I really hope this gets fixed because I switch between beta and normal commonly to try new features then come back to play servers.

And thank you if this got fixed...