Activating the Ender Dragon causes the Realm to Lag.

We recently purchased a Realm for our lovely community and not so long ago, we chose a day for us to enter The End. Once entering it automatically lagged the entire game and we tried multiple approach. Seems like when ever the Dragon gets loaded that when the Realm decides to completely crash. Many of us spent ton of quality of time on this world and it would be a shame to delete it due to one simple game error. Please help us figure out how to approach this and fix it.