Users not able to Save and Submit the Purchase Orders

In version 12 instance of the same user are unable to save/submit the purchase order form, while others are able to submit successfully. We have attempted to modify role permissions, but this has proven ineffective. We also assigned permissions to users who can submit the form, but this approach has not resolved the issue. Please assist us with this query if anyone has any ideas.

ERPNext: v12.4.3 (version-12)
Frappe Framework: v12.2.1 (version-12)

Console Error : -
Failed to load resource: the server responded with a status of 500 (Internal Server Error)
Uncaught TypeError: Cannot read properties of null (reading ‘exc’)