I was playing in a superflat world and I had paused and my phone's screen turned off as I was not using it when I turned it back on, and closed the in-game menu it was randomly raining (probably a coincidence) and strange red smothery textures appeared on blocks I built but not on naturally generated blocks. I pressed the save and quit button and the word Minecraft appeared normally as if I was normally exiting the world but then it started flashing madly. I closed the tab, reopened Minecraft and it's okay now. I have a Huawei P10 lite. I hope you can fix it.