Weird textures appearing "randomly"

This bug might be triggered by something, or it may be completely random. At least, I can say it isn't triggered by the nether.

Steps to reproduce :
-Play the game normally
-Keep playing until it happens

To go back to normal :
-Close the app
-Kill the process
-Reopen the world

Device : "Soshphone 4g"
Generic ZTE phone
Android 4.4.2

Everything below this line may be unrelated to the bug

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-What I did :
-I placed 30 boats in the nether using MCPE-14345
-I entered the nether. The game crashed, but I didn't think this was worthy of a bug report in itself, because it seems to have already been reported. Plus, it often happens without the last part of the bug.
-I reopened the world and entered the Nether.

Steps to reproduce :
No idea. I tried to do it again, but it didn't work.

What I expected to happen :
I would be in the Nether

What happened :
-Netherrack looked weird in a radius of about 16 blocks
-I placed a redstone torch, and it looked strange too
-Going back to the overworld didn't fix anything
-More blocks were affected (white clay was red, droppers had a black face, cobble had a bad texture...)
-After leaving the world and coming back, everything was normal again