This is an easy fix as you can see where you fell down on this most recent job: availability and deadlines. Answer VMs quickly and meet deadlines come hell or high water and, assuming you continue to produce quality work and are vetting your clients before accepting job offers, you should be able to get better feedback going forward and raise your JSS.
It is possible you were scored on the low side in other factors on private feedback, but given the fact that your client publicly listed these two, they were obviously pretty big issues. Your client actually did you a favor in showing you where he was really dissatisfied. These are such easy issues to fix. Don't bite off more than you can chew, answer your clients, and be serious about deadlines. Done. 🙂
