To resolve this, follow the steps below:
1. Identify the custom form used on the Non-Inventory Item.
Note: This can be seen on the Non-Inventory Item record or if the Custom Form field is not shown, the user may edit the form to show the Custom Form field.
2. Navigate to Setup > Customization > Entry Forms.
3. Find the Non-Inventory Part form used.
4. Click Edit link beside the form.
5. Uncheck the Store Form with Record box.
As per Field Level Help guide, check this box to store this custom form with each record entered with this form. This ensures that your records are viewed and edited with this form regardless of who is viewing or editing the record.
6. Click Save.
7. Edit the Non-Inventory Item record.
8. Toggle the Custom Form field and select the custom form modified.
9. Click Save.