Glitch after digging strait down at the seed

I found a glitch after digging strait down at the seed -5082156891300789959 in bedrock, pocket edition's trial chamber seed template. I thought I should see the nether.
 All the netherack was replaced with note blocks. I looked at a bastion and a fortress before heading to the structures in the overworld. I found the bug when I explored a cave. Weird texture swaps and some textures are completly changed into something else. Torches into torchflowers, iron bars to iron blocks,  shroomlight to white shulker boxes, and more.
I went to a stronghold and a trial chamber. I restarted the world and the whole texture swap was gone. I couldn't get it back so I couldn't give more details.
most textures were swapped with others. I took some photos and videos.