when using /summon EnderDragon it wont show its boss bar and it seems to act odd, like it will stay still then start moving foward.
https://www.youtube.com/watch?v=D9GPSc_Q_Ts&feature=youtu.be
a video to show what i mean. (ignore the last little bit i forgot i was updating a driver)
Environment
os: windows 7 64 bit
java: Version 8 Update 51 64 bit
Not a duplicate of MC-83239
Duplicate of MC-82911 - not fixed.