As mentioned in the changeset text, I've been updating WI halls to add in the wikidata reference (to hopefully help future users find all such halls).

This particular one has previously been mapped in detail to show the roof shape etc. I added the brand:wikidata tag into the relation, however JOSM advises that the relation has errors.

I searched the internet to find the error, but couldn't work out the fix. I'd be grateful if someone could fix it (and explain what needs to be done so that I can fix future similar issues should I find them) - Cheers!