Error when trying to register new Drupal account using same email address as billing address in CiviCRM

Attempted to register a new user account in Drupal and received the following:

<div class="crm-section">Database Error Code: Duplicate entry '19725-1' for key 3, 1062</div>
<div class="crm-section">Additional Details: <p><pre>Array
(
[callback] => Array
(
[0] => CRM_Core_Error
[1] => handle
)

[code] => -5
[message] => DB Error: already exists
[mode] => 16
[debug_info] => INSERT INTO civicrm_uf_match (domain_id , uf_id , uf_name , contact_id ) VALUES ( 1 , 161 , 'jaymcgraw@yahoo.com' , 19725 ) [nativecode=1062 ** Duplicate entry '19725-1' for key 3]
[type] => DB_Error
[user_info] => INSERT INTO civicrm_uf_match (domain_id , uf_id , uf_name , contact_id ) VALUES ( 1 , 161 , 'jaymcgraw@yahoo.com' , 19725 ) [nativecode=1062 ** Duplicate entry '19725-1' for key 3]
[to_string] => [db_error: message="DB Error: already exists" code=-5 mode=callback callback=CRM_Core_Error::handle prefix="" info="INSERT INTO civicrm_uf_match (domain_id , uf_id , uf_name , contact_id ) VALUES ( 1 , 161 , 'jaymcgraw@yahoo.com' , 19725 ) [nativecode=1062 ** Duplicate entry '19725-1' for key 3]"]
)

</pre></p><p></p></div>

Checked Civi and there was a contact already with the same billing email address, not marked as primary. It seems to be only when it's the billing email address as trying to replicate this with a duplicate contact work email address, not marked as primary didn't throw this error.