Are you operating STP or RSTP (valid for the complete network), or MSTP (individually on each VLAN configured and active)? Either way, the lower the priority, the greater greater chance of becoming the root. When I have it right, Netgear does define the STP priority (misleadingly named "Configuration Revision Level") to the default 32768 when I have it right. You can adjust in steps (increments or decrements) of 4096.
