I play Minecraft bedrock edition on an iPad, and I have recently encountered a bug involving horse armor. So I tamed a horse in a creative mode world and tried to put diamond horse armor on it. The inventory slot looked like I had put horse armor on the horse, but the horse did not appear to have the horse armor on. I played this way for a while, and the horse armor never showed. I came back to Minecraft later and went into the same world, and NOW the horse armor showed.

The same problem happened again, but reversed. I knew at this point if I put horse armor on a horse, it wouldn't show until I had saved and quit the game, then rejoined. But this time I used another horse with iron horse armor on it. I tried to take off the horse armor, and the horse armor returned to my inventory, like it's supposed to. But I could still clearly see the iron horse armor pattern on the horse. Once again, I could temporarily fix this by leaving the world and joining again.