Fix NetSuite SSS_INVALID_SUBLIST_OPERATION Error

How to fix SSS_INVALID_SUBLIST_OPERATION

1. 1Check how the record was loaded: record.load({type, id, isDynamic: true}) enables the dynamic-mode line APIs (selectLine, commitLine, getCurrentSublistValue, setCurrentSublistValue); without isDynamic true, use the standard array-style APIs (getSublistValue, setSublistValue with an explicit line index) instead.
2. 2Do not mix the two styles on the same sublist in the same script; calling commitLine on a record loaded without isDynamic, or calling setSublistValue with a line index on a record you are editing via selectLine, is the most common trigger.
3. 3Before any getCurrentSublistValue or setCurrentSublistValue call, confirm the immediately preceding call was selectLine, selectNewLine, or insertLine for that same sublist id.
4. 4Verify the sublist id itself is correct for the record type and current form; open Customization > Forms > the transaction form > Sublists tab, or check the record's schema in the SuiteScript records browser, since a mistyped sublist id also surfaces as an invalid operation.
5. 5For insertLine and removeLine, confirm the line index is within the current sublist's line count; removing a line number that does not exist throws this error rather than silently failing.
6. 6After commitLine, always call save() on the record; a commitLine without a subsequent save leaves the edit uncommitted and can cause confusing follow-on sublist errors if the script continues editing the same sublist.
7. 7If the sublist is a matrix sublist (item options on assembly or kit items), use the dedicated matrix sublist APIs rather than the standard line APIs, since matrix sublists have their own column-and-line addressing.

The selectLine-before-read rule

var rec = record.load({ type: record.Type.SALES_ORDER, id: soId, isDynamic: true });
rec.selectLine({ sublistId: 'item', line: 0 });
var qty = rec.getCurrentSublistValue({ sublistId: 'item', fieldId: 'quantity' });
rec.setCurrentSublistValue({ sublistId: 'item', fieldId: 'quantity', value: qty + 1 });
rec.commitLine({ sublistId: 'item' });
rec.save();

Common pitfalls

• !Loading a record without isDynamic: true and then calling commitLine or selectLine, which are dynamic-mode-only methods.
• !Calling getCurrentSublistValue before selectLine or selectNewLine has established a current line.
• !Copying sublist code between record types without checking the sublist id is valid on both.
• !Mixing standard-mode setSublistValue-by-index calls with dynamic-mode selectLine edits on the same sublist in one script.
• !Forgetting to call save() after commitLine, then continuing to edit the sublist as if the change had already persisted.
• !Using standard line APIs on a matrix sublist, which needs its own matrix-specific methods.