Can't add ssh key (exists as deployment key, possibly in deleted repo)

Hi. When I try to add another ssh key to my account, I get an error

Someone has already registered this as a deploy key.

I checked all my repositories and there are no deployment keys in any of them. I can only assume that this is the same problem as mentioned in Issue BCLOUD-8568: I might have used the key in the now-deleted repository "dotfiles".

I tried using the REST API to delete the key manually but that just gives me a 404.

Could you please check if the there's a deployment key associated with my account and delete it? I can supply the pub key via PM if necessary.

Thanks a lot.