When using forms to add to a list (where the code can be entered), users can accidently re-enter an existing code which triggers a model roll back, as it's considered a duplicate.
There's also no notification the model is rolling back so it looks like the app is spinning its wheels. This leads to confusion and potentially the user trying again (to no avail and another roll back).
Ideally, there should be some form of exception handling to prevent this scenario, including,
- notification that the code is already in use, and
- the option to accept that the data (inclusive of parent-child relationship) will be updated, or
- the option to cancel the process from running all together.