I suggest you take some photos, make a clear diagram, or whatever else makes the situation easy to describe to someone who has never been there. What are the dimensions of the remaining space for turning? There are Australian Standards that describe how much turning space is required to get into a parking space. Reference to an objective standard could help since one persons very tight space is fine for someone else.
(We marked parking spaces at 2.6m in one parking area so we could accommodate 8 cars rather than the 7 that habitually parked there using 3m each. 2.6m wide exceeds the minimum in the standard. There were some grumbles but people seem to manage now.)
In the ACT an individual can apply to the tribunal for “a declaration … that a resolution of a general meeting or executive committee meeting is void for irregularity”
If the motion was not on an agenda distributed to all owners you would have a good case, or decided at a meeting for which insufficient notice was given, or the class of resolution was insufficient to grant an exclusive use (perhaps in NSW a by-law adopted by special resolution-fewer than 25% opposed I believe).
Additionally or instead you could argue that use of that space by anyone as a parking space interferes with your reasonable use and enjoyment of the common property (I assume NSW by-laws use that formula or similar). The resolution above could be irregular for its inconsistency with the by-law. In this case your use and enjoyment of the common property would be the reasonable use of gaining access your garage.