MR6500 dropping connection

I live in an area where only cellular Internet is available and I had a cheaper netgear lte modem for a couple years until I decided, I wanted to upgrade to 5G Internet. I’ve had the new modem for a little over a year and when I was using it as a router, I would have to reset my switch every few hours to get a new device to connect to the Internet but as far as my LAN everything worked fine. I thought maybe AT&T was able to see that I was using more than five devices so I purchased an MR90 6e wifi mesh router and disabled ipv6 on the modem. First problem is that ip passthrough wont give any ip to the router so I left the router on on the modem and setup the mr90 to use a static ip with the nat ip from the modem and all was fine for several hours until I went to bed and woke up to the modem not connecting to the router. I tried switching the new router to dhcp but the modem would not assign the router an ip (dhcp is on on modem). After resetting the modem all is working fine (for now) with no settings change. I’m using Ethernet on the modem and the wifi is disabled; battery is out. I have read many articles of people having this same sort of issue and I’m hoping there is something you guys can do to help me resolve this. I’m network+, security+ and have 12 other network/security related certifications so it’s not like I’m new to networking and have tried everything I can think of including plugging the modem just into a laptop and leaving that on overnight only to wake up and have the same exact issue; internet says it’s connected to lte (won’t connect to 5g even with a new sim) but I can’t ping the modem and it kills the lease on my laptops ip. If I set the laptop to static ip I still can’t ping the modem until it’s restarted. Please help me