Thank you for the information!
In the logs, I can see that the internal modem is constantly detaching and re-attaching, so the device will most likely have to be RMA'd.
But before that, I'd like you to perform a modem update, as there are newer versions available. To update the modem, please follow the procedure described here. Please keep in mind, that a stable external WAN source will be necessary for this procedure. It is recommended to perform this procedure using firmware version RUT9_R_00.07.02.7.
Let me know if the update helps!