There is a capacitor in the CAP which retains programming. If it has reached the age point for failure, you could experience flaky behavior like you have seen. As curlycord suggested, get another CAP and test. You may not have a SAPS on the CAP at all, as you have stated. However, the wall wart may not be at the desk and may be back in the phone closet by the KSU and the power running down pair 2 or 2 and 3 on the drop to the M7324 jack. Just suggesting that if you have not looked in where the KSU is for a SAPS, it may be lurking in there tucked in a corner outlet or hidden outlet strip. I have seen SAPS tucked in the oddest places and they do not give any outward sign of failure, you need to throw a meter on them. I am pushing that angle a bit only because in my experience I generally see a SAPS whenever I deal with a CAP or KIM or KLM.
Also should ask are you sure no one had an errant cup of tea or any kind of spill ? The flexible printed circuit sheets will provide all kind of crazy results if wet.