1. I hope you have written GlideRecord on "sn_hr_core_task" and not "HR_task" in the above script

2. Open the BR "Validate Changes" on "sn_hr_core_task" table and comment these two lines. It will stop the rollback of work notes of HR case from being copied from HR task back into HR case

The sys_id of this BR OOTB is fa5330019f22120047a2d126c42e70f9