Hi,
Unfortunately, that wasn't a good fix; it made the tagging worse rather than better. The tag leisure=horse_riding is for complete riding centres and not for arenas or other things that may belong to a riding centre. See https://wiki.openstreetmap.org/wiki/How_to_map_a#Riding_centre_(equestrian) and example https://www.openstreetmap.org/way/291296002#map=17/45.382300/7.745034&layers=P . A node is also ok, example https://www.openstreetmap.org/node/5896012696#map=19/45.319560/7.934745&layers=P . Arenas should be tagged with leisure=pitch + sport=equestrian. In JOSM you use the preset for sport=equestrian.