Deploy Key gets deleted after some time

Hello,
if I create a new Deploy Key via ([POST] https://api.netlify.com/api/v1/deploy_keys/) and add the public_key to Github, everything works fine. But if I wait some time or create a new site which use this deploy_key also via API, the deploy_key gets removed and stops working. Also a GET request to the url above returns

Could you let us know the site name where this happened and the timestamps (along with time zone) when this happened?