I locked your thread because we already have a thread for the issue and we don't allow duplicate threads for the same topic
I do realize this is a serious issue, but I myself am not a developer, nor am I actually an employee of Re-Logic, 505 Games, or Engine. Moderators are all community Volunteers for Re-Logic
I do apologize for making you feel I'd run away, my day job is very labor intensive and I've had to work many hours in the last couple days so I've been too exhausted to address forum matters. I have actually presented this problem directly to the friends I've made at Engine, the solutions I've offered are just general guidance and my best guesses, like I said before I'm no developer so I don't know why this is happening.
I wish I could do more to help but as a moderator, I'm already doing all that I can.
It does allow you to do this, I've done it myself several times
You go to your settings > storage> (select device which contains Terraria) > Games and apps > scroll down to and open Terraria's files > Select your world file there should be a prompt near the bottom of the screen for what to press to open it up and select "Copy", "Move", or "Delete"> choose "Copy" > select an alternative storage device to copy your saves to.
It appears this doesn't solve the issue though :/
I do apologize
It sucks when you've put so much effort into something and then something ruins it. I suggest you don't delete that world however, the next update this Holiday season (Between Oct and Dec) might, hopefully, fix it. As far as 505 responding, they're currently doing a major overhaul to Customer Support, Quality Assurance (bug testing), and Community Management (involvement). So you might not hear back from them for quite some time as writing up and then implementing this major changes will take some time.