I have been using Dropbox and Boxifier for PC along with Dropsync for Android to keep my worlds in sync between my Galaxy S4 with 0.14.0 Beta 6 and my Windows 10 laptop with v0.13.1.

Before joining the beta, I turned off the sync so that I could work with worlds on my phone in the beta without making them unplayable on my laptop. Later, I chose to "restore" all of the worlds on my phone by just copying the older versions of them on my laptop. I made sure to completely get rid of the world files from my phone and then copy the world files from my laptop. I figured that this should have worked fine because the worlds that were coming from my laptop were technically just versions of the worlds my phone had before I joined the beta (my phone had v0.13.1 if I'm right, as well as my laptop).

The problem is that now on my phone, with random worlds that I restored, I get an error that says "[World name] can't be opened." The affected worlds will still open perfectly fine on Windows 10 though.