I have following queries.

My condo handed over by developer a year ago and it is still within the defect liability period. When raining season, the car parks is flooded with water and the JMB which consists of resident members have talk to developer on this numerous time. Yet, the developer is like besok lusa and keep saying will look into it and never come back with an action/ rectify the root cause of the flooding issue at car parks.
Need valuable advice on what can be done against the developer? Seek external party to rectify it and claim the cost against developer? or....?