Suggestion if you're seeing Real weirdness.
If you're on Faceplant, do a backchannel message to the Mothership with your last name and last 4 of your number. Use the speedtest page that shows the last 10-12 tests not just one test. It's easy to load the pic of the multi test page to Faceplant. I like to do 2-3 tests at once and get most of a full day on one page. That way you get tests in different traffic times.
Just tell em it's a FYI.
My speeds are higher here now but still has BIG swings. (1.5-6.5)
A Major issue is the UL speeds which being < .20 Mps the speed test doesn't even want to finish.
You have the tech and it's pretty easy to shoot Das Mothership some useful data.
Bruce in Ocala, Fl