Whenever a property completes it is normal to find small issues that need rectifying. New buildings need time to settle and dry out, and in the process small issues may arise which need attention.
This process is called snagging and the initial rounds will be undertaken by the developer as part of the completion process. By the time you complete and get the keys for your property this process will either be completed or underway.
For larger issues following completion and handover, warranties are in place on all new buildings which will cover these.