Hi Hans,
Please have a look on https://taginfo.osm.org/keys/mapillary:image#values or better on https://taginfo.osm.org/keys/mapillary#values. I know (since recently) these keys, but only know the difference by studying the wiki for this answer. That's why I couldn't correct the error on my own. According to Wiki, however, the url would not be necessary on the value page either .

Met vriendelijke groet / Mit freundlichen Grüßen

Georg V.

