I asked the customer about the installer, and he had no idea. I moved the system from one location to another about 4 months ago, but there were no changes to the system, although in retrospect, had I attempted a "just in case" backup I would have discovered this issue then. Anyway, I thought it was a one-off request (not a regular customer), but then a month ago they asked for an additional extension, which I provided, but again, no need for any programming. Now this request for an additional line.