MC7304 - Error 633 - Windows 8.1/10

Good Afternoon,

I have a problem with Modem MC7304 and Windows 8.1/Windows 10 Pro (x64)
On Windows Startup, I execute an Internet Dial-up connection and after that I execute a Dial-up VPN connection

Everything works fine as long as the modem will lose the signal; than I get 633 error (Port already in use) and I have to restart Windows to reconnect.
The problem seems does not occur with Windows 7.

To simulate the signal loss, I unplug both antennas “Main” and “AUX”

I have installed the latest modem drivers and firmware.
I tried to close Internet and VPN dialup connections and restart RasMan process but I still get 633 Error
In this state if I change modem COM port and disable and re-enable Modem in Windows Device Manager, Internet and VPN connections works fine again. So I suppose that some service or driver lock the COM port.

If I execute “devcon restart ‘USB\VID_1199&PID_68C0&REV_0006&MI_03’” command when connections are active, I receive “USB\VID_1199&PID_68C0&REV_0006&MI_03 Restarted” response and Internet and VPN connections start working again after a few seconds.

If I execute “devcon restart ‘USB\VID_1199&PID_68C0&REV_0006&MI_03’” command during “633 error”, I receive “USB\VID_1199&PID_68C0&REV_0006&MI_03 Requires reboot”.

Then, I suppose modem drivers lock Modem and his COM port.

Can you help me? I can not ask the customer to restart windows or change COM port while on the job.
Thank you in advance and excuse me for english

Anyone can Help me?

Thank you