A few pointers, but no direct, specific answer:
- See first post here to disable ALG in your router, it may address the dropped calls but not the random reboots:
http://www.obitalk.com/forum/index.php?topic=33.0- Your VPN is presumably between your computer (i.e., you start a VPN client in/on your computer, not on your router, yes?) and your work network, therefore other devices attached to other ports on your router are not on nor affected by the VPN (other than the obvious having less bandwidth available). I'm just stating this so you know.
- You can look at the reboot times via either: 1) The ObiTalk Portal, or 2) Web Server-Based Local Configuration (also called The OBi Device Management Web Page also called direct IP address interface), via Status > System Status > Uptime. You'll have to enter expert mode to see this via 1). Caution, these two means to look at the device config trip up new users all the time. See
this, and best advice is at first stick with the method, 1) or 2), you used to initially setup the device.
- You can commiserate in this thread, although your config, only one SP "slot" in use, does not match the two others (me being one of them) discussing the same issue:
http://www.obitalk.com/forum/index.php?topic=5275.20-Independent of the dropped calls issue, and lacking anything obvious to you, I'd suggest you log a trouble call with Obi Support for the mystery reboots. They can, for example, examine your configuration via the ObiTalk web portal (assuming you configured it via this method), setup sys logging, etc.
EDIT to add: Reboot reason codes. These codes appear in the System Uptime field, such as '12 Days 8:58:48 (6)'. See the list
here under Reboot Reason Codes. If no code appears, then that is a true Mystery Reboot, if you see a code try to determine a cause. Sorry, I should have remembered this as the first item to look at.