HI there,
So I would ask are the WAP /router you connect to on the same circuit or in different rooms?
Silly maybe have you checked the IG on the Plugs (the third prong) the computer is plugged into?
Are these on Battery or on USB-C ?
I’m suspicious of the WiFi on the S3 being handled by the 2 core, seems this wifi lib may not be up to it. The C3 works perfectly, The BSP’s may be why also. how many have been tested?
What happens if you attach a test clip from ant outside to ground?
I’m sure if you test and eliminate things it’s not you will figure it out…
HTH
GL 
PJ 