Document won’t sign with custom js Field validation

Hey there!

I have a PDF with a signature field (created in InDesign) and custom Java Script field validation added in Acrobat. After adding the js validation code Acrobat won’t trigger the signing process when clicking the signature field, alerting me the document can’t be signed in its current form and suggests to save, re-open and sign again – which does not work.

This is my code – altered for demo purpose:

function test () {
    app.alert("Test function got called.")
    event.rc = true
}
var myFormField = this.getField("myFormField")
myFormField.setAction("Validate", "test()")

Removing the script let’s me sign as expected.

Am I missing some additonal steps to allow siganture fields and custom field validation to work together?