Have any of you tried updating the firmware to your home WiFi routers?
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There are very old and extremely generic instructions provided here. For example, it hasn't been possible to downgrade iOS (especially to 8) for a very long time. All of these suggestions assume the phone is at fault. Try to power off/power on the home WiFi router, or make sure the router has the latest security updates / firmware updates. A lot of home routers suddenly freeze or partially crash when many devices are connected or too many of them are downloading at the same time.