Device: Xiaomi Redmi 1S 1.6GHz Quad-Core 1GB RAM
This rarely happens between 30minutes to 1hour of gameplay, Almost all blocks and items changes their textures to another, Inventory textures applies as well. (Screenshot = Bedrock to Pumpkin etc)
I've always set my CPU clock frequency to 300MHz min - 1.0GHz max to prevent overheating also to save battery's life so i guess maybe lowering down the CPU clocks causes the game to slowly reload the textures again after storing them for a long time (RAM Cleaning) ?