Intermittent loss of internet since upgrading to gigabit

I previously had 300MB Blast internet.  In December(2020) I upgraded my network to use a Motorola MB8600 modem and a TP-Link AX6000 Wifi-6 router.  This system worked flawlessly for 2 months.  Last week I switched to Gigabit internet, and now it seems that I am frequently lossing internet.  It was occuring once a day, but after a rtechnician visit I lost it every 2 hours.  The only way I could recover was power-cycling the modem.  Xfinity phone rep supposedly "re-provisioned" with a signal, and that lasted over 12 hours, but have required 2 recycles today.  Modem lights all show functioning, but router indicator showing no internet.  However, once again power-cycling router does nothing, I have to cycle the modem.  It is curious that this behavior corresponds to move to Gigabit,