Merlin, thanks for your fine work.
May I suggest that you number your standard answers and publish the list - so when people ask the same question for, say the fourth time, you can just answer with the relevant number.
I did the factory reset, got the app analysis back - but then after pressing Apply - either on the QoS page or the Bandwidth Monitor page, can't remember - back to only "General" traffic ??
I second that - tried everything, but only getting "General". I also tried "painting" my computers (red for "Highest, orange for "High" etc.). No difference.
Have you recently stayed in hotel with a really lousy WiFi? That used to be much better the year before? Now we know why. No offence intended, but please think of other guests.
121 is still a work in progress - maybe 95 pct. finished. QoS now works, but you cannot restore a saved configuration.
You can flash from Merlin's firmware, but start by resetting to default values.
Power on with WPS pressed 30 secs in case of problems.