I have a MAX BR1 PRO 5G on version 8.5.3 and with an internet SIM everything is fine. However, with a Verizon and T-Mobile private APN sim with no internet the device connects fine but after a couple hours the router becomes unresponsive. A physical power reboot solves the issue.
I tried turning off the WAN failure detection, tried setting a ping to an internal network IP (which works but router still becomes unresponsive) and a factory reset to no avail. I tried setting the service from Auto to LTE and same thing.
Maybe the router just randomly became malfunctioning as it is happening with two different vendors…or I must be missing something?