@zlone
Is it possible that the TP-Link extender is introducing noise into your electrical power? Similar to what dimmers do in home wiring?
Are you using any power conditioners?
Ethernet Wiring
I prefer to use a hard connection as opposed to using Wi-Fi. Our basement is finished off, so my only access point requires me to run the Ethernet cable through approximately 25' of HVAC ducts. Is this okay? The cable would be inserted into the duct about 15' away from the furnace plenum. Thank you.