Subject: EC200U-EU (EC200UEUAAR03A22M08) - module resets during outgoing voice call + VoLTE not available (Bouygues Telecom, France)

Hello,

I use an EC200U-EU USB modem (USB ID 2c7c:0901) for SMS and outgoing alert calls.
Firmware: EC200UEUAAR03A22M08 (sub-revision 01.300.01.300). IMEI: available on request (private message).
Operator: Bouygues Telecom (208/20), LTE B20, RSRP -86 dBm.

Setup
- Host: Proxmox VE 9.2 (Debian-based, kernel 7.0.14-pve). The modem is plugged directly into a USB port of the host (xHCI). The host loads the "option" and "cdc_ether" drivers (ttyUSB0-6).
- The AT port (USB interface 02) is exposed through a udev symlink and passed into an unprivileged LXC container (Debian 13) with a bind mount and a cgroup rule for character major 188.
- Inside the container, SMS are sent with Gammu and voice calls are made with plain AT commands on the same port. The two never use the port at the same time (file lock).
- When the module drops from USB, the device node disappears, so a udev rule on the host restarts the container after the module re-enumerates.

Problem 1 - reset during voice call
After ATD<number>; the call is set up in 2G/CS (+CLCC: 1,0,2,...), the remote phone rings, then about 6-10 s later the module drops from USB (all ttyUSB ports disconnect). It re-enumerates first as 1782:4d12 and then as 2c7c:0901. This is 100% reproducible. SMS works fine. No over-current or USB error in the host kernel log.

Problem 2 - audio configuration
AT+QAUDSW? returns 1, but AT+QDAI? returns 3,1,1,4,0,0,1,1 (ALC5616, slave mode), and there is no external codec on this board.
AT+QDAI=1,0,0,4,0,0,1,1 returns +CME ERROR: 902.
AT+QDAI=1 returns OK, but after AT+CFUN=1,1 the value is back to 3,1,1,4,0,0,1,1.

Problem 3 - VoLTE
AT+QCFG="ims" returns 1,0, AT+CIREG? returns 0,0, AT+CVMOD? returns 3. AT+QMBNCFG is not supported. Calls always fall back to 2G.

Questions:
1. Is the reset during CS calls a known issue with this firmware? Is there a newer EC200U-EU firmware that fixes it?
2. How can I set a valid audio configuration with no codec (or no audio at all) so that it persists after reboot? Could the ALC5616/slave setting cause the crash?
3. Is there an EC200U-EU firmware with VoLTE/IMS enabled and the Bouygues Telecom (or generic French operators) profile? If so, how do I get it and flash it? Can it be flashed from a Linux host?
4. What is the peak current required during 2G calls, and is a standard USB 2.0 port (500 mA) enough?

Attached: at_trace.txt, kernel_usb.log, module_status.txt.

Thank you.
