Hello.
Please remember that when you are mapping for this project 149, by default it hides all the buildings layer, so you do not see the complete OSM data. This building that you added already exists as way 247445606.
You can press "F" to open map data panel and there re-enable buildings layer to see everything.

I went ahead and deleted your duplicate. 👍
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            Published using OSMCha: https://osmcha.org/changesets/149592822
            