I was going through old worlds and I noticed a few worlds that had not been opened since March 2017 (3/24/17 was the date for uploaded world). Opening these worlds show that my hot bar has been replaced with Block id 255 in stacks of likely 255 (shows 99+).
To reproduce
Get a world not opened since March 2017
Open world
Notice inventory filled with info reserved.

I would expect my previous hot bar from that time to load.

This affects both creative and survival worlds, non of which have been edited with a third-party editor.

Device: Samsung Galaxy S4 Android 4.4.2