@Clive_A The error comes up when almost any setting is changed on the router, even when it doesn't strictly speaking involve the switch. In addition, as of this morning, I now have multiple issues...

@Clive_A No, the config is the original, not imported from another device. It's been a while since it started happening, but I think it might have started when I updated the firmware on the SG2008P...

@gerba I have this issue too - worked fine for ages, and suddenly it gives this error after any change to any aspect of the setup.