purple se connection problems

tl;dr: My firewalla stopped working yesterday.

I've been having periodic internet connection issues which always resolved themselves either on their own or after a cable modem reboot.  I was on 400mbit service.  I decided to ask for a new cable modem to see if it would help, and they talked me into 1gb service when they did the exchange.  When I made the exchange they told me my signal levels were good.  I forgot that my purple SE maxes out at 500mbit.  

Yesterday the internet went down and I looked at the firewalla app and it turns out the internet has gone down for less than a minute 5-10 times per day for the last 7 days (or more, not sure).  I started moving things around trying to connect to my cable modem to get to the status page (never got in) and when I gave up and reconnected everything, I still had no internet and couldn't get to the firewalla.  I tried connecting just my access points to it, no dice.  I kept rebooting things and would sometimes get a push message on my phone saying "Firewalla is back up!" and if I went into the app it would still not connect to the firewalla.  Every once in a while I could get to the firewalla in the app for a little bit, but then I would lose it.  And the whole time it had no internet access.  I eventually gave up and connected my old (omada) router and got the internet back.  

Could this be caused because of my 1gb network speed?  Do I need to upgrade?  If so, is there any kind of trade-in program?  I've only had the purple SE for a year and a half.  

If that's not the cause, does anyone know what else it could be?  Is my purple SE broken?

I have a Spectrum E31T2V1 DOCSIS 3.1 cable modem feeding the purple SE set up as my router, which then feeds a managed switch and omada access points.  

Thanks