In cases where you can show that it's a common property fault, then the OC should pay for the damage (not just the excess).
The question of the security gate is a little trickier. If it says in your by-laws that the OC takes responsibility for making the carpark or building secure, then you have a claim.
You may still have a claim even if it doesn't say that but it might be harder to prove. For instance, if the Executive Committee had known the gate was insecure and had made a decision to do nothing about it, I reckon you would have a strong claim. But if your by-laws say that vehicles and goods are stored at owners own risk, then you're up against it.