Connection is very sluggish with some wifi router in the presence of congestion

[Yuri]

I observed the problem using a laptop with FreeBSD 11 with TP-LINK 
device TL-WDN3200 (N600), driver if_run, at one location with these two 
routers:

Xxx  a0:3d:NN:NN:NN:22    6   54M  -27:-50   100 E BSSLOAD HTCAP WME
  - good quality
Xxx  a0:3d:NN:NN:NN:0d   48   54M  -25:-48   100 E BSSLOAD HTCAP VHTCAP 
VHTOPMODE WME
  - very poor quality


Whole lot of other people were using wifi in the same room. I assume 
most of them didn't have any problem.

When my laptop connected to the second router, connection was extremely 
slow, to the degree of being unusable.

The first router though worked fine, I assume other people were equally 
distributed between them. S:N ratios were fluctuating so that the second 
was stronger at times.


Is it possible that VHTCAP VHTOPMODE have something to do with the problem?


Yuri