This happened while I was talking on vent and playing.
If you click on the delete button and then start flying you will fly upside down.
so: Just press delete, then start flying,( u will fly circles) when u think you are on the right positon to fly, drop "delete" button and u will fly upside down.
I think this is server side cuz friend saw this, but dnnw sure.
Or it could be ur vent button, dnnw, I have delete to talk on vent.