iPhones won’t connect to network

“I have an Arris XB7 gateway. Multiple iPhones connect to my home Wi-Fi, work normally for several minutes, and then lose internet access while still showing connected to Wi-Fi. The same iPhones work perfectly on another Wi-Fi network/personal hotspot. Other devices in my home continue working normally. I’ve already restarted the gateway, forgotten/rejoined the Wi-Fi, tested 5 GHz separately, and tested different DNS settings. I need you to check the gateway provisioning/firmware and investigate the XB7 or replace the gateway if necessary.”