Apologies for a delayed response. To clarify, when executing a USSD command, the message is sent to the mobile operator, and the response can take up to 3 minutes. During this process, the network connection may temporarily fall back to a lower technology (3G/2G), which can impact the VPN connection.
Could you confirm whether the VPN tunnel reestablishes itself once the device reconnects to 4G?
Hi. I have a similar issue here. Firmware 0.7.11.3 works normally. After upgrading to 0.7.12.x I could not longer send ussd commands using the web interface. I downgraded to 0.7.11.3 and ussd works as expected now.
Perhaps the original bug reporter could downgrade to 0.7.11.3 and that might solve this issue temporarily.