Hi,
The tag leisure=horse_riding is not a building tag. You have removed building=house from https://www.openstreetmap.org/way/1226912053, Therefore this building is no longer rendered as a building. The tag leisure=horse_riding is for the whole area of a riding centre, like here: https://www.openstreetmap.org/way/438965728. Compare https://wiki.openstreetmap.org/wiki/Tag:leisure%3Dhorse_riding.

Similar problem here:
https://www.openstreetmap.org/way/1006397320
https://www.openstreetmap.org/way/1006395562