I am using AT&T on a MAX HD1 Dome CAT18 and a MAX Transit CAT18 and have not seen this happen. My plan is through Nomad Internet, and I have been using the SIM/connection for the last 3 weeks without issue continuously.
The plan is a membership/pre-paid through them, and is designed to be used in a hotspot or mobile router.
I’m in the San Juan Islands in northern Washington State if that helps in terms of regional issues.
I am also using a DNS Lookup Health check, and have this connection as part of a SpeedFusion tunnel for redundancy. I’ve seen it fail for other reasons (signal level) but never gotten into a situation where it has passed health checks and not passed traffic or some other hybrid.