Halo 3 Covenent (Bravo) Trapped inside bubble

I cannot A: Gain altitude when flying. B: Move around the area without hitting ‘invisible’ wall, nor can I return to the beach (starting point) without running into an invisible wall. Regarding altitude: I cannot even land on the first little island (the one with a large gun placement) even if I go to the backside where it is the lowest. Am I missing something?