I did this before to go against Sime Darby some years back, actually the same sister company of SP Setia.
Initially I complained like hell to the Customer Service but in the end, I found out that they are not in power when it is about rectification costs between developer and contractor. So beh tahan these people.
So I got hold of all the defect pictures from all the residents and asked Customer Service to organise a meeting between their architects, consultants, township head and site people. CS is more than willing to help cos they kena bombarded every day. So they siam to the consultants and their bosses.
I showed them in Powerpoint slide by slide. At the end of the 30th slide, they surrender and set up a rectification team. And very important is the residents must turn up in full force to show support and add in the verbal complaints. It turned the screw on the developer and it did solve a of our problems. Not 100% and not everyone is happy but most of us got what we paid for.
We even threaten to ask the press media to come in. No point go legal as once it go legal, all project people will wash their hands and leave it to the legal team. Developers got plenty of money to play ping pong. House owners do not get to renovate their units and the clock is ticking on the defects liability period. Remember the contract is between individual house owners and the developer. Everyone's problem is different from other neighbours. Everyone's willingness to accept the defect is also different.
Good luck.