It's been happening for a few days now. While download speed appears to mostly be fine (~930Mbps), upload speeds are very slow.
I was seeing 5-6Mbps upload yesterday, today seems slightly better between 20-40Mbps. But it's a long way off the 930Mbps I should be getting.
BQM graph looks "OK", some pretty continual packet loss along the top, although it appears small (the spike was me rebooting the router to see if it changed anything).
Example speed test, from a wired device. https://www.speedtest.net/result/c/1470166d-2959-4302-a82a-09e2f91ff70f