Problem: Chunks missing everywhere I've built on a world, but it's not due to corrupt data. It's due to the latest update to v1.14.1

Background:

I created a world using MCPE.

Regularly back up this world by copying it's minecraftWorlds folder to thumbdrive.

After v1.1.14.1 update, this world went from 80Mb down to 2 Mb and large chunks are missing.

Closed out ouf MCPE, deleted the shrunken world folder and copied my world backup back to it.

Opened MCPE again and loaded the world, but same problem exists

To ensure it is NOT a corrupt data issue, I copied that same backup to minecraftWorlds on my desktop (Windows 10). It loads fine and everything is as it should be.

The world has been entirely created in Survival Mode. All my achievement are correct. My sign-in info is correct. 

The only other odd symptom is that after the update, MCPE generated a minecraft pillager outpost right in the middle of something I was building. As soon as I start walking toward it, the chunks disappear, and I seem to die from being attacked. After respawning, I'm back at the original default coordinates with all my building progress lost to the default world map.

I also tried loading this on another android phone (which has NOT updated-ed yet) andthe world loads fine on that device. I also loaded it on my son's android phone (which HAS been updated to v1.14.1) and the same problem occurs.

Help Request:

If this issue is due to a configuration change that was forced upon me during the last update, please provide instruction to reverse it.

If it's a bug, please tell me the version that was current in July 2019? And how do I install the older version on my Android phone? And how would I turn off updates until there's an update to fix this issue?