I replied to your Reddit post. But so others here know, it's an issue with eCSFB and IMS on the Airave. Devices which maintain SRLTE don't have the issue, since calls and texts go over CDMA instead of LTE. I have a ticket open about it, but so far they can't find anything wrong. Been a problem that has been ongoing for months, and I know other people in different markets with different devices and accounts have the exact same issue. It affects all phones that rely on eCSFB and IMS instead if SRLTE.
A "solution" is to block the LTE ipsec tunnel on your router's firewall. In my experience, blocking access to 184.108.40.206 and rebooting the Airave resulted in just CDMA and no LTE. That being said, if your non-SRLTE phone can pick up the macro LTE signal at all, it will almost certainly never use the Airave. I don't believe that macro eCSFB will setup a call via the Airave.
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