To reproduce this error use UIBuilder @v6.7.0 or later.
Use initial/default uibuilder installation, install vue in the library, use supplied template 'Vue3 no build step, ESM Client, Vue module'.
This page is rendered:
Enter some text in the text field (for the '....when you exit it' input box) and press tab.
The event is fired and the 'Data from front end' msg is received in nodeRED. However the payload.value=false.
Do all necessary to remove uibuilder and reinstall uibuilder directly with npm in .node-red directory:
npm i node-red-contrib-uibuilder@6.6.0
repeat the above tests and payload.value will contain the entered text.