One must make clear that developer shall appointed different contractor for different project, ya developer has their representative (clerk of work) to monitor the progress of the site, and make sure the work is in order, however the main contractor is the key party to ensure quality work to be delivered.
Look at Bdr Kinrara, for the last 19 yrs of development, they have at least 15 main contractors (+ many sub-contractors) to build the houses, the quality of each project also different, like BK5 Desiran & Sentosa, I rate 8 (less than 3 defects averagely), BK9 Cahaya or Spektra, I rate 5 (20-30 defects), BK5 those old 20x70 near the mosque, I rate 2 (worst than the Mah Sing one), however BK5 4C7 old phase quality was good.
I also heard that TMS M Suites or M City in Jln Ampang has many defects, at the same time Perdana 2 in Selayang is very good quality.
KR has a few contractors, frankly say 2 & 2 1/2 storey are behind time now, that's why they are rushing for it, the quality of the end product is in doubt, whereas the rest hv to comply to CONQUAS std, shd be better in quality.

Which project is this? Obviously the quality is bad.
Aman Perdana and Subang 2 also so so