I've checked all of the other tracks, and couldn't find any other instances of this problem, so it's unique to Fern Bay.
To me, it seems like there is oversized collision geometry around the upright section of the gantry that encroaches through the barrier. Is collision geometry even required here? The barriers would normally prevent hitting the ironwork from either side, and the only foreseeable way of actually hitting it would be if the car was already airborne and jumping the barrier. I note that when driving behind the spectator wall, none of the other track furniture has collision geo, so these particular ones are unique.
I tried to repro this one too, and couldn't either. The replay would be useful to have.