I conducted a test using two rucks P300. The AP distance is around 20 cm and they face same direction each other. The result of speedflex showed about 20Mbps. But when the distance is about 5m,10m 20m, the results showed more than 100Mbps. My question is that why when the distance is very short, the speedflex result is poor?
It might be the result of low SNR,
Due to both signals are strong enough to the device you are testing , so noise level is very high.
One thing you can try by changing manually the band channels. like in one of it, set the 2.4 GHz channel to 1 and in another set it to 14, and same for the 5GHz band change the channels and check the result.