SQM only reduces bufferbloat in one direction [WRT3200ACM]

This indicates that your CPU might actually scale back its frequency, believing there is nothing to do. We have seen several times that CPU frequency scaling does not wrk well with SQM (even though at your line rates that should not matter and certainly it should not cause delays in the 400ms range). It would be interesting if you could try to disable CPU scaling and see how/whether that affects the shaping?

seems like something else is afoot, maybe try a different browser to test.

I don't have any spare cables, but I'll add this to the list of things to try.

I could be wrong, but I don't think CPU scaling is supported in this build. The /sys/devices/system/cpu/cpufreq/ folder shows nothing.

I just tried the speed test in Chrome and it's giving the same result as Firefox.

In my original post, I said I didn't notice this problem in 18.06. I am tempted to go back to that version to see if it was my imagination. :thinking: Maybe I should also try one of the "Davidc502" builds that seem to be pretty popular here.

try at least unplugging the cable and replugging on both ends. Also potentially try swapping two cables that you have in use, just so maybe the "bad" one is in a different place. For example if you swap a WAN and LAN cable then if the new WAN cable is good, WiFi should work, whereas the computer connected via LAN will have problems.