Gigabit Speed Issues - Don't Accept "The network is congested"

I have had ongoing issues with maintain gigabit speed.  Multiple trips by techs etc and replacing modems, cabling and actually removing an amplifier.  The one common thread seems to have been related to provisioning.

When I lose gig speed I drop down to what appears extreme+ and downstream pegs right around 650-660 but I generally still see gigabit layer uploads (around 42mbps).  Losing gig speed has happened (looking in modem and router (pfSense)) when the data harvester loads int he modem logs and/or a power cycle of the modem.  The recent fix (had worked the last two times since early March) was a reprovision.

So now I have fought the battle again, call CS, yes me again, read the notes in my account and kindly reprovision the modem.  Have to go through all the steps so they can get to the point where they can reprovision.  Unfortunately, this time, the reprovision doesn't work.  Get escalated to Level 2, same thing, reprovision doesn't work.  Get a call this morning from a very unhelpful more senior tech that said my issue is just due to network congestion.  Said signals were fine and be happy with 600 Mbps.  I am kicking myself for not getting his info and if anyone from Comcast cares I am sure they can find out who it was.

SO, now to the fix.  I tried a factory reset of the modem.  Guess what, back to gig speed.

So for some of us out there who are more IT inclined, have had m,ultiple expeicirnces with the same issue, don't accept "it's network congestion" if you think something else is at play.  I want to determine if this is a fault of the modem software or what.  Maybe it is time to go back to owning (like a did with Surfboards in the past until I needed an MTA for phone).

EDIT:  XB6 modem...