Just wondering if you loaded the latest Beta that I posted about?
What city are you located?
So when your testing 2.4Ghz, are you testing with mixed modes or single mode like N only on manual channel 11? Test with radio output on High and Medium? I've seen some other users with the 890L report that they had better experiences with the radio set for Medium. Can you try this?
What devices do you have connected on the 2.4Ghz radio?
If it comes to this, I would make contact with support and ask for an RMA and you can even do this, as for a cross shipped unit. They will ship you a new unit and then you ship your old one back. They'll charge you if you don't send the unit back. This would give you time to test the new unit out and see if it corrects what your seeing with your current unit.
only in 2.4g wifi the 5ghz and lan i'm getting full speed
by the way i called the support and all what told me to update the router . i told him i already updated it . then he told me to bring the router to their location which almost 4 hours driving.