Upload control in repeater, can’t upload pdf

I have a kirki repeater control container a few controls, one of which is the ‘Upload’ control.
However, when I use it to try to upload a pdf it doesn’t work properly. It appears to upload the pdf, but it doesn’t show in the media screen. I can still ‘Select’ it from the upload as it appears in the right hand column, but when I then save the customizer and refresh it doesn’t save it.
A normal Upload control works fine, but in a repeater it doesn’t.

I found someone had a similar issue here:
https://bleepcoder.com/kirki/351101763/upload-control-in-repeater

But there is not a solution on that thread.

I’m wondering if this is a known bug or if I am doing something wrong with my implementation?
Thanks in advance!

My code is as follows:

Kirki::add_field( 'kirki_repeater', array(
    'type'        => 'repeater',
    'label'       => esc_attr__( 'Links:', 'kirki' ),
    'description' => esc_attr__( 'repeater test' ),
    'help'        => esc_attr__( 'This is a tooltip', 'kirki-repeater' ),
    'section'     => 'test-repeater',
    'priority'    => 1,
    'settings'    => 'repeater_test',
    'default'     => '',
    'fields' => array(
		'pdfupload' => array(
		'type' => 'upload',
		'default' => '',
		'label' => 'upload pdf',
		
		),
    ),
) );