I disconnected a couple of days ago in the end and when I rejoined, I was able to fly. I did not activate using the fly command, i just had it. I have fly (not fly+) and it was enabled in the main world before I logged off.
These are the screenshots. I was not able to recreate this bug. I left and reentered to try and fly was gone.
The black box is me just covering my coordinates.

 

Okay thanks, was confused