Bench migrate error: Incorrect date value to a column that shouldnt be date

When I use the bench migrate command I recieve the following error:

Incorrect date value: “assign_to_sales” for column “_ds4fsaf4s6d8f”.‘tabNotification Recipient’.‘reciever_by_document_field’ at row 1

This happened after setting notifications on a specific doctype item creation to a linked “assign_to_sales” User. I don’t understand why the “Incorrect date value” if the reciever_by_document_field isn’t a date type.