The Kyocera DIGNO Keitai 4 has a specific issue linked to third-party SMS apps where the apps have issues receiving texts. The behavior is such that when an alternative app is set as the default other than the stock “Mail” app or Google Messages, the phone will never receive texts while the app is not running¹. This seems to be directly linked to the specific CPU that the phone has, as a MediaTek process will delete the SMS in this scenario, citing that the app is not “whitelisted”².