Hi @amansingh,
It seems like some of the users from your account list is owner of some sources.
You need to remove that user from source owner, add someone who is not part of the source for which you want to perform account reset.
I know you have mentioned there are no correlated accounts but please make sure it is not the case.
Usually you will see the details in response, if possible share the response.
You can check below post although it is with regards to deprecated API, but the issue is similar as yours