Read-only custom fields lose their value when cloning a Record
|Knowledge Article Number||000193776|
When you clone a Record, custom fields that are Read-only for the user cloning, will lose their value when the new record is created. For example:
This is currently working as designed, since read-only fields are not sent to the server when a case is cloned. This doesn't affect admins since they have the "Edit Read-Only fields" or users who have edit access via Field Level Security and Pagelayout Setting.
Note: This does not affect Standard fields on the case like the Account or Contact lookup field.