Hello Thomas,In my case, it was pfSense Linux firewall connected to the WRVS4400N...We changed the ISP modem during the troubleshooting and as a result, the tunnel was always up at both sides. In both modems (the original modem and the new one) we us...

I have exact the same problem as you.I even did contact Cisco but the first level technician was unable to sole it and his answer was that the problem is at the other side where I have Linux firewall (pfSense).Probably you can open a case with Cisco ...