There would seem to be a problem with the Oneninedesign (RPI2) case breaking the RPI3 Wifi hardware circuit.
This is a view of the problem area. The circuit from the wifi chip (the black thing next to the SD card) goes to the filter (White thing with spot on it) via a couple of resistors, then a decoupling cap before it passes through the board to the antenna on the other side.
Moving into closeup
The decoupling cap is 8.5 mm from the board edge and 4mm from the board end.
Now for the case
There is a standoff centered at 8.5mm from the edge and circa 6mm from the end under the board.
So, the standoff will probably (did in my case) snap of the decoupling cap and possibly the resistor behind.
So if you have RPI3 wifi probs and a RPI2 type Onenine case Like the ones sold in RPI3 kits (like I bought from PiHut) then there is a good chance your problem is the case breaking the hardware.
Cos I believe it broke mine !
So I invite comments from the RPI design crew and others to check and verify my findings.