No internal network i.e. no DUT network? The network bridge init ran without error.

What is the purpose of the access point for wired connection? Why not connect the DUT directly to the moblab? Are you using it as an ethernet switch?

sometimes I do a physical network between AP and DUT so that AP just act as a switch. 

Same problem happened again. DUT have trouble connecting to wifi, indicating that the moblab internal network probably has some problems. 

Deleted: moblab_logs_Ylc9O0.tgz 3.7 MB

moblab_logs_Ylc9O0.tgz 3.7 MB Download

I found these mobmonitor warnings:
{"health": false, "name": "UsbEthernet", "actions": [], "description": "No USB ethernet device detected. This may indicate that no DUT (or some other important device) is not connected."},
{"health": false, "name": "DutExists", "actions": [], "description": "No DUTs were detected. Please plug in a device for test."}

Can you check your moblab side USB dongle? Looks like it might have flaked out.

I will check my ethernet USB dongle next time. It has crashed before, so it's likely. 

Are there more details on the USB dongle crash?  I think Grant can help steer us at a stable device there.