Hi Geeks

I'd like your help on the next step finding a workaround for this problem. I'm not familiar enough with NZ fibre or this model router so I'd love your input.

Ok I have 900down, 500mbit no cap up slingshot fibre. Its great. Except for one isolated situation:

On 2.4Ghz wifi only, YouTube only, the connection is absolute crap.
In fact its the media from youtube that stops working. The text on pages and stuff comes through, but with missing thumbnails and videos periodically pause.

Youtube on ethernet: fine.

Other sites on wifi: fine. 

The WIFI's physical connection is solid. There is no wifi interference and i can happily browse other sites on the 2.4GHz while youtube is choking.

It also happens on more than one device: and iphone and an android. Now a PC hooked on to the 5ghz wifi is just fine from what I've seen.

I've phoned up slingshot and if you saw the other thread I briefly described the service droids i suffered through until a third rep advised that theres a firmware problem with the modem they give out marked as giving these symptoms.

My questions are as follows:
How can I disable any brain damaged processing the slingshot router is doing to the packets? I am thinking does this modem try & fail at QoS?

Does anyone else here have this issue?

Can anybody think of creative workarounds? 

And considering this is a known, persistent fault - shouldn't slingshot have an obligation to provide a working service? Shouldn't I be made aware of this problem before spending money?

And when i report the symptoms, are the reps properly reporting the severity of the problem to management? Considering I went through two staff members that should have known to attribute my connection's symptoms to the known fault - I'm not dismissing the possibility that this is worse than believed or reported.