We have migrated from v 11 to v12. All the custom print when modifying is giving the above error.
Print Format Type cannot be "Server". It should be one of "Jinja", "JS"
Are you still facing these issues?
i also facing such issue.
@Gavin_Ji check custom format check box select any option from the type and save.
Then uncheck the custom format and save again
Thank you so much. This one did the job for me