I've had this setup a couple years. Recently, the TV shows a poor HD signal when streaming Amazon HD content,causing a poor picture. Setup shows a strong Wifi signal.I tried a LAN cable from the wifi roter to the tv,no change
WIFI signal doesn't mean anything, it just says connection between PC and WIFI router good, that's all it means. The Internet, where your program is coming from is beyond the WIFI router.
Are you the sole user (of the Internet)? because other people in the house can "steal" Internet bandwidth from you.
Both the wife and I have phones that may be using wifi,and I have a tablet that sometimes uses wifi,but those devices rarely stream video,so I didn't think it would be enough bandwidth to cause any issues.
I will try it with the wifi on the devices turned off