From your description, it sounds like you are probably having a power issue. We typically recommend budgeting around 1A per standard servo, and it sounds like you are right at that range. You might consider using multiple power supplies, each powering its own bank of servos. The picture below shows where you can cut the VSRV power rail to split it into separate banks that can be powered separately:
You could try a higher capacity power supply if you have one available; however, please note that the traces on the Maestro power rail can handle about 6A. Since you are above this anyway, you should probably still separate the power rail into banks to prevent higher currents from passing through them. Alternatively, you could power the servos separately from the Maestro as long as you still have a common ground to complete the circuit.