When AWS management account discovery is configured, Discovery creates DynamoDB records (which are only configured on the management account) on the child service accounts.
These duplicated DynamoDB records should not be created.
The issue happens when the credential of management account is used on the child account.
Please make sure the credential field on child accounts is correct.
In most cases it should be empty for child accounts (e.g. you are using assume role from management account, or using IAM Profile).
However you can also set credential for child account if the credential is created in the IAM on the child account.
You may refer to documentation below to configure AWS management account discovery: