In the change record, when user add new work notes and click on post button, system automatically advancing workflow and skips entirely all the current approval activity steps, for example, user or group approval activities.

Checked all Script includes like "WorkflowApprovalUtils" if it is in OOB state.
The issue was caused only for the non-admin users and works fine for the admin users.
Checked of there are any business rules with current .update which might be causing the issue, but none found.
Checked all business rules running on the update. None found.
Custom query business rules is causing the issue.

Since it is on the update of the record, there was a business rule causing the issue.