PPOMOOL That helped for me, but after using it like this for a while, I noticed glitches, and while performance wasn't nearly as bad as before (simply unusable), performance still wasn't robust enough.
I tried a bunch of other settings, but could not find anything better. So I've decided to do what I was trying to avoid: a full factory reset of the router. It's a pain in the butt, as you have to rebuild the whole configuration, but eventually, it got me to a place where it appears, connections are fast and stable, and even using the 160 MHz bandwidth, which I can confirm is active ("channel width" value in the "Quest link" tab of Settings).
Let's see if I can confirm that performance is good over a longer period of time. So far, so good, but I'm more reluctant to declare victory, since yesterday did not turn out to be the way it appeared at first.
I've updated my router's firmware many times since I bought it (Current Version : 3.0.0.4.388_23925-g269b2a6): maybe the settings truly needed a reset to get the right updated default?
