Now that it's happening, it happens in any new or saved world. The game is functionally bricked for me
I just had this issue on android 1.2.13. Everything had been fine. I was doing a lot of fishing and the fish button stopped working. Just after that this same issue of mobs - spiders, horses, etc would disappear when close. Bubbles still appeared for the spider in the water and it would do damage. I couldn't mount a horse or kill a cow without it disappearing. Mined blocks also stopped dropping things and I couldn't eject a CD from a juke box. All these glitches started together.
Closing and restarting the game seems to have fixed it for now.I'll try to recreate