Networking

I have a NSA 2400 SonicWALL that is our main firewall at our home office. We have one tempermental TZ 170 Enchanced SonicWALL at a remote location. From the remote location to the home office we have two VPN's - we have two because we have to segment our wireless traffic that goes back to our ERP server at the home office so we can be PCI compliant. When the TZ 170 gets rebooted by IT or if that location loses power and the TZ 170 gets rebooted that way, the VPN we have for the wireless traffic will not come backup. The only way we have figured out how to get that VPN back up and running is by rebooting the NSA 2400. The problem is, we don't want to reboot the NSA 2400 firewall during store hours because it will take down all 20+ remote stores. We usually will just reboot the NSA 2400 at night and the next day the wireless is working at the remote location. 

Does anyone have any ideas on why only 1 of the 2 VPN's will come back up at the remote store when the remote firewall is rebooted? If more information is needed, please let me know.

Thanks,

Luke