I have found at least one page where wikidata displays the wrong coordinates, although it has the right value. Check this page. If you read the coordinates, the API returns 42.1206, 2.76944. This is (42∘ 7'14.1600", 2∘46'9.9840"). However, the page displays 42°7'19"N, 2°46'24"E. This can't be a rounding error.
If you click the link on the right, it takes you to the GeoHack page, which shows the right conversion on top of the page.
Another example: Sant Pere del Burgal. There's a mismatch between what the page shows, and what's actually there.
So, it really looks like a conversion problem in the wikidata page.