Cannot save or close HR cases

Cannot save or close HR cases. Below error message:

onSubmit script error: TypeError: Cannot read property 'display' of undefined: function() { saveAllSelected([ gel(id) ], [ gel(ref) ], ',', '\\', '--None--'); }

Any

This can be caused by duplicate variables on the form

Usually caused by a custom widget or business rule and scripts

1) Check the variables on the form if duplicated.

2) Remove the variable editor on the form 

How to Configure Form: https://docs.servicenow.com/csh?topicname=configure-form-layout.html&version=latest

OR

1) Remove duplicate variables by going to the [question_answer] table - https://<instance_name>.service-now.com/question_answer_list.do

* This table is where the submitted Record producer variables are stored

2) Filter table_sys_id=<record_sys_id>

3) Check if there are duplicate variables and remove the duplicates in this table

If you are encountering the issue on REQ/RITM/SCTASK, the variable submitted are stored in the tables [sc_item_option_mtom] and [sc_item_option], so you can check these tables and remove the duplicates here instead