3rd January 2017, 8:19
Haha oh dear me that's so funny! Thank you -- i can't believe that it is solved, & so easily. I hardly ever use FF, but for the past few weeks have been randomly launching it whilst troubleshooting something. As i'd never heard of that FF extension [not plugin, actually] due to my unfamiliarity with FF, i'd never in a million years have thought of that as the culprit / solution. I almost didn't even bother making this topic, as i imagined nobody would know. Phew.