ZDK.Client.showConfirmation() and showAlert() silently fail on Boolean/checkbox field onChange - anyone else?

ZDK.Client.showConfirmation() and showAlert() silently fail on Boolean/checkbox field onChange - anyone else?

Hi community,

I've been trying to show a message pop-up when a checkbox field is ticked. I'm using the onChange event on the Opporutnities create page. 

function onChange(value) {
  if (value === true) {
    ZDK.Client.showMessage(
      "Note: Message goes here.",
      { type: "warning" }
    );
  }
}

Setup:
- Field Event, onChange, on a Boolean (checkbox) field
- Create Page (Standard), Opportunities module
- Script executes successfully (confirmed via the Messages panel — showing Success at 0.00s)

Issue:
Despite the script executing successfully, no dialog appears. I tested with showConfirmation(), showMessage() and showAlert(); nothing displays anything visually, even though all log as successful in the IDE. 

For comparison, I have an identical setup on a text field (Opportunity Name) using showConfirmation(), and that works perfectly.

What I've ruled out:
- Cache (hard refresh + incognito tested)
- Script not being enabled
- Wrong API field name
- Page vs field event configuration

Has anyone successfully got showConfirmation() or showAlert() to display from a Boolean field onChange event? Is this a known limitation? Any help appreciated.

Thanks