Thanks ost - but I have tried it both from direct physical keyboard and SSH using this command. I’ve been reading a few other problems related to this issue but all seems to come down to “not installing as root user”. Which i’m not - I’m installing as pi. So still scratching my head here.

I found that not placing the default calendar module directly below the clock this helps stop the repeating. However I could not find the root cause of the problem.

OK i think i’ve solved it. magic mirror HAS to be started (npm start) from a terminal window in the x-window server. you cannot start it over ssh.