Dear Newbie,
The short answer is that if the owners corporation undertook repair work to the common property, and in the course of that repair work, lot property has been damaged then the owners corporation is responsible for remedying this damage as its agent, in this case the window repairer, caused the damage.
Similarly, if a common property defect such as water penetration causes damage to lot property such as carpets then the owners corporation would be responsible for repairing the consequential damage to the carpets.
In your situation, the owners corporation should insist that the contractor who conducted the window repairs comes back to site to repair the damage caused. Keep pushing!
All the best,
Makinson & d’Apice