Is this happening on Realms? That used to happen to me on Realms, I would turn off the server then change it then turn the server back on.
lol I realized after posting. I'm a disaster today.
Oh sorry, I thought it was a required field. Will be more careful next time.
Looks like this issue has been resolved on iOS MCPE 1.1
It's happening on iOS 10.2.1 as well.
Is this happening on Realms? That used to happen to me on Realms, I would turn off the server then change it then turn the server back on.