Huawei E303 3g modem stuck in a wrong USB mode

Question

I have a USB 3g modem (Huawei E303) running well for weeks now under Linux (Raspbian Jessie) as an isolated box prototype that serves web content over WiFi to mobile phones and tablet pcs (for the background). I've configured udev to change it's mode from 0x1f01 to 0x1001 on plug-in, connection comming correctly, disconnecting cleanly on un-plug, etc.

Today I made a wrong action. Probably an AT^U2DIAG=0 I think. From there it is stuck in mode 0x1c05, identified as an E173s (modem on). And no way to switch it back. I've tried to un-plug / plug-in (even under Windows, that does nothing), I've tried to usb_modeswitch back, I've tried to AT^U2DIAG=1, wich gives a +CME ERROR 50.

Mar 11 16:46:07 raspberrypi kernel: [  421.900561] usb 1-1.2: new high-speed USB device number 6 using dwc_otg
Mar 11 16:46:07 raspberrypi rsyslogd-2007: action 'action 17' suspended, next retry is Fri Mar 11 16:46:37 2016 [try http://www.rsyslog.com/e/2007 ]
Mar 11 16:46:07 raspberrypi kernel: [  422.001682] usb 1-1.2: New USB device found, idVendor=12d1, idProduct=1c05
Mar 11 16:46:07 raspberrypi kernel: [  422.001710] usb 1-1.2: New USB device strings: Mfr=2, Product=1, SerialNumber=0
Mar 11 16:46:07 raspberrypi kernel: [  422.001727] usb 1-1.2: Product: HUAWEI HiLink
Mar 11 16:46:07 raspberrypi kernel: [  422.001742] usb 1-1.2: Manufacturer: HUAWEI
Mar 11 16:46:07 raspberrypi kernel: [  422.003096] usb 1-1.2: bad CDC descriptors
Mar 11 16:46:07 raspberrypi kernel: [  422.003441] usb 1-1.2: bad CDC descriptors
Mar 11 16:46:07 raspberrypi kernel: [  422.007329] option 1-1.2:1.0: GSM modem (1-port) converter detected
Mar 11 16:46:07 raspberrypi kernel: [  422.007840] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB0
Mar 11 16:46:07 raspberrypi kernel: [  422.008900] option 1-1.2:1.1: GSM modem (1-port) converter detected
Mar 11 16:46:07 raspberrypi kernel: [  422.009306] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB1
Mar 11 16:46:07 raspberrypi kernel: [  422.010174] option 1-1.2:1.2: GSM modem (1-port) converter detected
Mar 11 16:46:07 raspberrypi kernel: [  422.010687] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB2

If I manually call pon, the chatscript connects the modem, that is immediatly disconnected :

Mar 11 16:31:21 raspberrypi pppd[6851]: Serial connection established.
Mar 11 16:31:21 raspberrypi pppd[6851]: Using interface ppp0
Mar 11 16:31:21 raspberrypi pppd[6851]: Connect: ppp0 <--> /dev/ttyUSB0
Mar 11 16:31:22 raspberrypi pppd[6851]: Remote message: Greetings!!
Mar 11 16:31:22 raspberrypi pppd[6851]: PAP authentication succeeded
Mar 11 16:31:22 raspberrypi pppd[6851]: Hangup (SIGHUP)
Mar 11 16:31:22 raspberrypi pppd[6851]: Modem hangup
Mar 11 16:31:22 raspberrypi pppd[6851]: Connection terminated.
Mar 11 16:31:22 raspberrypi avahi-daemon[418]: Withdrawing workstation service for ppp0.

Please tell me if you need more logging, I will paste it here.