Multiple Kerlink Gateways showing as offiline

We have a large number of Kerlink gateways that became unconnected in the last 5 days, with many disconnecting 4 or 5 days ago. Was there any kind of back end TTN problem? Simple reboots does not correct the problem. These gateways reboot themselves every midnight via a cron job in any case.

Changing the server address to something different (on the Gatweay), rebooting, then changing it back again and rebooting again does , bizarrely, seem to fix the problem.

Is it the case the the server address on the gateway DOES NOT NEED TO MATCH that defined in the TTN console? That is the behaviour we are observing.