Well there's a lot of stuff happening all at once, and without a bigger picture, I can just give you some basic steps on how I would start debugging:

• Make sure the new untagged interface is actually working as expected (check rx/tx, basic pings)
• Try pinging the devices ONLY from that interface
• Check the configuration of the devices if you can contact them and see what endpoint they think they are supposed to be talking to
• If the are WiFi, make sure that wireless network can be pinged from this new interface (join a laptop and ping back and forth)
• If all else fails, snoop that interface and see what IS traversing it