iPhones get finicky when they connect to a WiFi network that doesn't actually provide internet access. While it says it connected to the WiFi you want it to connect to, it can occasionally disconnect from that network and connect to another saved network in range in search of internet access without notifying you. I have solved this before but only by removing the saved networks on the phone so that the phone's only WiFi network choice is the MTH Network.
By some rare odd ball chance is your layout located near your home Wireless router? Perhaps close enough to used a an Ethernet wired connection between your DCS Explorer (via USB -> Ethernet dongle) and your home router?