GS1900-24HP Disabled Ports continuing to provide power and temporarily routing traffic

I have a GS1900-24HP running 2.40(AAHM.0)C0 on which I had disabled two specific network ports upon the departure of an employee (and, yes, the config file was saved when the change was made). A couple of weeks later, a new employee started and was able to plug in the previously used PoE VOIP phone, get power, and even use it for several days before finally calling to report that the phone had "stopped" working (no dial tone, but phone still had power).
In addition, the MAC table shows the USG60W, which is connected on Port 1, as being connected on Port 14 as Static Unicast. The switch serves only a single network, so everything is on default(1) VLAN. Several ports are configured in QOS, but nothing extraordinary. The MAC table, however, is also showing devices on other networks that are connecting wirelessly as though they are on Port 1. Those wireless devices connecting through the USG, and on SSIDs that are configured on an entirely separate subnet - one with security policies that should be preventing visibility of the network the switch is on (which I can confirm by trying to access that network).
This device was only installed about a year ago. Up time is currently at 66 days. 
Am I looking at a failing switch? Or can anyone else confirm similar problems?