Thank you for raising the question. Can you please confirm about the source type you are trying to create the account in ?
Do you see the create account operation defined in the source if it is not a standard connector.
Also, could you please share the features available on the source ? You can get this information by making a get source by ID API call from vs code or postman.
No, i have not seen such issue. This sounds quite strange. Are you using the standard EPIC connector or using web service based source to connect to it (if that is possible).
But i do not have an experience with this source type so not sure about the issue.