After a periodic (daily) reboot some of our customers' RUT955 routers are not able to reconnect to VPN or RMS, due to "cannot resolve host address" errors. The mobile connection seems to be up though. I am not sure, if this is only a DNS issue or if there is a underlying routing issue though.
When turning the modem off and on again, i.e. sending mobileoff + mobileon via SMS to the routers, the connection does work again - most of the time. Affected firmwares vary, most of them in the 06.07 range.
We already tried a lot of workarounds, like setting manual DNS servers, ping reboot (which already caused some serious downtimes), etc., and are at a point where we cannot recommend these routers to our customers anymore.