Hi,
This was a bad idea. You have removed the building tag (building=yes). This is a building and therefore should have a building tag, otherwise it is not rendered as a building. You have replaced the building tag with leisure=horse_riding. This tag is for riding centres and not for buildings. If this building is a riding hall / indoor arena you can tag it building=riding_hall. iD does not have a preset for this currently, but in the next release it will.
Compare:
https://wiki.openstreetmap.org/wiki/Tag:leisure%3Dhorse_riding
https://wiki.openstreetmap.org/wiki/Tag%3Abuilding%3Driding_hall
https://www.openstreetmap.org/way/1008067851#map=18/53.66750/-2.74167&layers=P