API gets stuck when Hubspot does not accept email address

[startuptnt]

Hubspot email rules do not allow some emails to be entered into Hubspot, whether API or otherwise. When a user erroneously enters a wrong email, this Hubspot extension will try to add it but will fail with a 400 error:
"isValid":false,"message":"Email address xxx@invalidemail.con is invalid","error":"INVALID_EMAIL","name":"email"}],"status":"error","message":"Property values were not valid",

This in itself is fine, IF it unqueued the faulty registration, however, this is not the case. When the next ticket is purchased, it will try and add xxx@invalidemail.con again, and again. So 1 invalid email essentially blocks all future contacts from being added to Hubspot.

In my view, this is a big problem because I had thought that the integration was adding automatically and it had not been for over a month with no notification of failures. Additionally modifying the email in the attendees screen of each event GUI does not fix the problem.