end bossfight glitch les then 10s

the enderdragon takes damage without me doing anything.
i think it happen after all cristals where distroyed.
he begun to thake damage (started to flash a red tin) and died.
I repsawned him with clay and he again died but even faster.
it looked like a flying squid (on land/above water).

the pictures are from the 3the fight where he didn't even stand 30 seconds.
i re-did the fight, then i spammed the screenshots so u can see almost everything.
and i still get more eggs every battle.