Assuming this is the gate to the scheme’s parking garage, your Strata Committee is talking nonsense. Of course the garage gate opener is common property – if they don’t own it, who does?
Here are the fundamentals:
1. You are legally entitled to the peaceful enjoyment of your lot
2. A garage gate opener that’s excessively noisy is not operating correctly.
3. The owners corporation is legally obliged to maintain and repair common property.
4. The garage gate opener is common property.
I think your first option is to tell the committee to read the basics of strata law and do their job. Failing that, you can seek mediation at Fair Trading with a view to pursuing orders at NCAT under section 232 (2) of the strata schemes Act.
In very basic terms they can either repair or replace the gate opener now, or waste time and money fighting this, then have to do it anyway.
And if the resident bush lawyer on the committee argues some made-up law that means that the machinery isn’t common property, print this post and show it to them and the other members. Oh, and ask them, if it doesn’t belong to them, or anyone else, who will complain when it disappears overnight?