Note - This issue occurs with mouse usage but not when using a track pad.
Steps to Reproduce
Set the sys_properties com.snc.on_call_rotation.show_legacy_calendar=true.
Impersonate an ITIL user.
Navigate to On-Call Scheduling > On-Call Calendar.
Using a mouse (not a trackpad) right-click on a rostered member and select view span.
Note that instead of the read-only form of the cmn_rota_member record dialog, the Add Item dialog is displayed.
Import the attached cmn_schedule_page record.
Related Problem: PRB710917