v1.5.4 BMP issue in Beirut map

Hi Everyone, I have an issue whenever I play the Beirut map in single player mode,anytime I use either a BMP 2 or 3 as the gunner, the main gun shoots just fine however the machine gun does not shoot straight where the barrel is aimed.It always fires out about 90degrees from where it is aimed, making it useless.Is there some setting I am missing out on or is it a known glitch?
Thanx much for any help
Deizeldoo