After upgrade, On-Call schedules page is not loading.
Modifications to script include 'OnCallSecurityNG'
The behavior seen is due to the customizations to script include 'OnCallSecurityNG':
When using the On-call Schedules UI, the 'oncallgroups' scripted REST API is being called:
This eventually calls the method 'getManagerAccessForGroups' in script include 'OnCallSecurityNG'. However, do to changes made to this script include the method 'getManagerAccessForGroups' is not found in the script include.
The solution here is to revert 'OnCallSecurityNG' back to the out of box code.