That's z-fighting. it happens when 2 exposed faces are at the same position. in this case they are not in the exact same position, but I suppose minecraft for some reason has the map move a bit. I think to solve this you can use invisible item frames, but I am not sure.

here is the command for them if you are in java. If you are in bedrock I have no idea:

/give @s minecraft:item_frame{EntityTag:{Invisible:1b}}Hope this helps