This is the relevant piece of code:

console.log(transaction);

var inverterLine = transaction.findSublistLineWithValue({
  sublistId: "item",
  fieldId: "custcol_categorie",
  value: 2
});

//Inverter
transaction.selectLine({ sublistId: "item", line: inverterLine });
transaction.setCurrentSublistValue({
  sublistId: "item",
  fieldId: "item",
  value: inverter.value
});
transaction.setCurrentSublistValue({
  sublistId: "item",
  fieldId: "quantity",
  value: inverter.quantity
});

console.log(transaction);

log.debug({ title: "committing", details: "committing line item" });
transaction.commitLine({ sublistId: "item" });
log.debug({ title: "committed", details: "committed line item" });

console.log(transaction);

transaction represents currentRecord here

Have you tried setting the

forceSyncSourcing

parameter to true when you set the sublist fields.

Yesss thank you!! That did the trick! It makes so much sense, especially after what Sandii said earlier.