@SwiftOnSecurity
The weirdest I ever had was a cable modem acting up and giving awful speeds. I'd unplugged it from power numerous times without any success. The Comcast support person told me - even though I'd tried removing the power, to actually physically remove the coax cable for a few minutes, and I'll be damned if it didn't fix it!

Apparently their systems detect if the coax cable is plugged into a thing and won't FULLY reset the circuit so long as that cable is attached to a modem somewhere. I was dumbfounded, but it worked!