Mission Intensive Care Issues (Grand Theft Auto: San Andreas)

Ku, I went through gta san andreas, and then there was a problem, on a mission of intensive therapy, when you need to check 3 ambulances, I only have one, and then just nothing, and after a while the mission fails, due to the fact that the mafia left with Johnny, I haven't found anything like this on the internet, absolutely, who knows what the problem is?