Several of the blocks that i placed in the end cannot be permenantly removed and exhibit strange behavior.  They can be removed, but any reloading of the area will cause them to reappear, even while the item is in my inventory.  the issue only happens when the game is saved with those blocks, then reloaded, and even then it is inconsistent at best.  additionally, placing a block above or below the glitched block will allow you to permenantly destroy it, but the one that was placed above or below is then glitched, as long as it is below y level 16.  the issue persists with blocks such as torches and levers, respawning them attached to thin air if their support blocks are removed.