Vett93
This appears to be unique to your situation, when power is cut from the PE, APC, Shunyata Guardian, or the S/AC. each will require a re-stabilization period, but so will all other filter designs, including ferrite and choke based parallel designs. Cutting the power to the APC with the PE installed is no different from unplugging the PE or the APC from the wall. The APC by itself, without other forms of added filtering, will go through a re-stabilization period as the EL caps in the power supply charge. Circuit re-stabilization for any power supply is normal, component or PLC
for example lets say you own a balance power unit...the transformer inside the PLC takes 14/15 days to re-stabilize, pending the max amperage of the transformer vs. circuit size vs. system min and max constant draw pending amp and tv design. Component power supplies also go through a re-stabilization phase every time power is cut, normal power supplies take 48 to 60 hours pending the size of the power supply to re-stabilize, this is why manufactures mention a conditioning/break-in period when the component is first installed, it doesnt really matter what you label the interaction, adding any capacitor based power supply to an inductance based circuit is bound to create resistance in the form of odd harmonics, or in worse case scenario voltage drops until the capacitance, inductance, resistance balance of the circuit levels out and creates a stable magnetic field within the in-wall wire geometry, so to answer your question. it's not the issue that the interaction is unique to your situation, what you have to come to understand is that it's normal to experience a harmonic swing every time the system is unplug the from the main. Another thing to take a look at is added components to a stable circuit, adding anything from a DVD player switch mode power supply, to a pc UPS, to a digital alarm clock, to a lamp with a 40 watt+ bulb, will swing the circuit for a period of time until the circuit magnetic balance, were talking about the circuit electrical center of the in-wall wiring, re-stabilize and lowers harmonic ringing.
The basic PE design, like many other products, lower circuit inductance in order to damp the circuit, lower RF and EM interference, increase power factor correction, and control circuit ringing created by everything installed. All power supplies, including the APC and Shunyata , communicate to one another via circuit/capacitance leak back to the wall. In most cases the capacitance value of the leak is incompatible with other circuit/power supply design leakage, thus the continued search for audio nirvana, but the PE puts an end to the leakage incompatibility problem/circuit crosstalk by retuning the circuit through strength and frequency coverage. The distance strength of the PE basically overwhelms the power supply, circuit in-wall wiring, and component power cord wiring. The frequency bandwidth of the filter neutralizes odd harmonics created by circuit crosstalk, including non-a/v circuits. The PE also retunes the component power supply, including the APC, so all components ring at the same frequency, this is important, it is the best way to lower circuit feedback noise, interaction between components, and damp RF/EM fields. The side benefit of this type of filter design is a user tunable circuit, but that is a different topic that should be reserved for another day.
Regards
Alan Maher