Maybe the new update removed that?

Normally how many devices are connected to the router? Reduce the clients to test the router. Hang up the router using some wire to cool down the router.

Like a magic. If the issue happen again, better to contact TP-Link support for help.

Deco doesn't support hostname resolve.

Did you find the current firmware version? If the current firmware version is already the latest one, then it is normal to show no updates. Besides, there is another way to update if it is not the...

Place the bulb close to the router and update the kasa to the latest version. Reset the bulb by turning the light on and off 5 times, not 3 times.