After upgrading to Service Management 17.3 from 17.1 the behavior has changed related to "onchange" but it has not been documented.
Release : 17.3
Component : SDM - Catalog
Below is the documentation change provided by SE via defect DE61227:
onChange
Specifies the JavaScript function to run when the element value is changed.
Update to be done:
On Change triggers when there is change in Table model:
1.1. When new row added through Insert table (+) icon On Change is triggered as empty Row
Added to table,
1.2. Through table API's also On Change triggers
1.3. When user edits/removes table values On Change triggers
onSelect
Specifies the JavaScript function to run when Selection/Deselection of checkbox on table row. (On Select is applicable only on Table component only)