I have recently transferred worlds from an iPad 2 to my Windows 10 PC.  These worlds were created a long time ago, so they use the old limited world templates.  This was before more biomes were added to Pocket Edition.  Now that the worlds are running consistently on an up to date version of Minecraft, the game is trying to place new biomes overtop of old ones.  For example, the game is trying to place trees on top of trees, create mountains in midair, and create swamps in water.  Whenever I try to break these new blocks, they just respawn when I leave the area a few minutes later.  This glitch most often happens with trees.  However, there are a lot of areas in these worlds that have black shade around them, even if there are torches in the area.  There are times when I am unable to fly through the air because of invisible blocks blocking me as well.  This issue has been around ever since infinite worlds were added to Minecraft Pocket Edition.  I have had parts of a world on an iPod 4 running iOS 6.1.6 destroyed by this glitch.  Even though this was years ago, the glitch is still in the game. I do not have copy of the original world save, but the way to reproduce this problem is to load Minecraft Bedrock Edition in an update earlier than 0.9.0 as this was when infinite worlds were added to Bedrock Edition. Then, create a new world in this older version of Minecraft. I do not know if the seed matters, but both the worlds shown used the seed "gimmiecoolseed". Next, create and load the world. Once you have done that, exit the world and update Minecraft Bedrock Edition to 1.8.1. Then, the glitch that I mentioned earlier should happen. Please fix this issue as I do not want my older worlds getting destroyed because of this glitch.