Mode: Easy Survival, no creative or command manipulation

Ender Dragon spawned as expected in the end until after multiple deaths (approximately 5) when it disappeared (not killed) and portal to the poem opened. After poem was viewed, returned to overworld where large chunks of blocks were missing, primarily local to where I had mined and built settlements/railways.

Continued playing, believing this was a common bug and would have to respawn Jean to get the End City portal to spawn. Upon entering the Nether, the Ender Dragon was spawned there and large chunks of blocks were missing, again primarily local to where I had made settlement/rails. Made a creative copy of the world and flew to the Ender Dragon to observe behavior, and she appears to be acting as expected, but is taking out blocks as she tries to fly through things.