I've bought three birds this year, all from birdrooms which use half-height flights for their main flights. All three have broken their necks in my full-height flight, the first two at the start of the summer and the last today. I thought the last one was safe, he rarely got off the floor and I never saw him higher than the lowest perch.

I've not had any other bird break their neck, but they've either been bred by me or came from birdrooms with full-height flights. So be warned if you have full-height flights.