AT&T Fiber service continues to be unstable after several service technician visits

Good morning! I continue to have inconsistent and unreliable fiber internet service, despite five or six technician visits over the last six months. Technicians have replaced the cabling, terminations, the modem, yet we continue to have problems. The technicians will come, it will work for a few days, then become intermittent again. I performed a factory reset on my modem and had the same result. Sometimes we get NAB-3032 authentication errors, but I don't always have the chance to get the error code.

This is very disappointing because we had rock solid AT&T fiber service at a different address about a quarter mile up the street, where I made one or two service calls over five years or so. 

I need someone who can fix this service and make it stable. Otherwise, we will be forced to cancel our service. Thank you for any help you're able to provide.