How to restrict asset selection to only one in Service Catalog request form?

Hello,

We are using ServiceDesk Plus On-Premise, and we would like to restrict users to select only one asset when submitting a request through the Service Catalog.

We have tried using Field and Form Rules with the following script on REQUESTER.ASSET

var assets = $CS.getValue("REQUESTER.ASSETS");

if (assets && assets.length > 1) {

$CS.showError("REQUESTER.ASSETS", "Only one asset can be selected.");

$CS.stopFormSubmission();

}

This works in the browser console (we see the correct array of selected asset IDs), but the script does not prevent form submission, and the showError function is not consistently triggered.

We also tried onChange rules on REQUESTER.ASSETS, but that doesn't seem to fire at all — probably because this is a system field rendered as a component.