MC7455 QMI interface is unstable


I got a MC7455 in last week and trying integrate it to my board.
The OS on my board is linux 2.6.36.x.
The QMI driver I used is S2.23N2.31 and the SDK is SLQS03.03.08.
The module successful connect to LTE base station while I setup it by AT command.
But it seems unstable while I setup it by QMI port with the sample code in SDK.
It hard to bring up LTE session.
On today, I successful to setup it with QMI port once.
But, after that, I can’t get it work anymore.
Its PID change from 9071 to 9070.
Only ttyUSB0 created while I insert GobiSerial.
And no more qcqmi interface created while I insert GobiNet.
It seems there are very limited resource or info for MC7455 on Sierra Wireless.
Is there someone can give me some advises for such condition?

Ricky :question:

After turn off the power over night,
The PID revert back to 9071 now.
It is strange.
Additionally, I can successful connect to LTE base station.
The error I saw on yesterday seems caused by I ran udhcpc on usb0 interface first before start LTE session.
If I setup LTE session first then run udhcpc.
It successful connected.