When there is an ender dragon you are able to see it at any distance as normal, but when you go to another dimension, it ceases to be fully visible until you approach her within a radius of 64 blocks.
MCPE-174712
When entering and exiting a different dimension, the Ender Dragon is not visible.
Resolved
Duplicate
13
Linking to MCPE-174711 since these are nearly identical issues.