I'm getting a few reports from iPhone users that texts are not being delivered to Android and non-iPhone numbers. It seems iPhone-to-iPhone works fine, though. When users turn off WiFi on their phones, texts are sent via cellular to. But once WiFi is turned back on, texts are not being delivered to Android phones. I've adjusted the bitrate and dual band is selected.
I would Setup a group policy in the dashboard and turn most stuff off. Then apply it to one of these devices having issues. It will help to troubleshoot the issue of what is blocking it on the Meraki/Wifi/Network side.