Form does not submit when file field has validate.required true

My form definition includes the following 'file' type filed. I have found that if the validate required part is there then the form will not submit, ie I click the submit button and nothing happens. Alternatively if I remove those two lines then it all works as expected. Any tips on where I should start for debugging this?

Note that the form loads and renders fine. Even the red asterisk shows up on that field when I include the validate required true.

    -
        name: photo-c-card
        label: 'Add a picture of your c-card'
        type: file
        multiple: false
        destination: user/data/membership-application-form
        accept:
          - application/pdf
          - application/x-pdf
          - image/*
        validate:
            required: true

It's a known issue actually, tracked in https://github.com/getgrav/grav-plugin-admin/issues/887

There is no solution at the moment, other than removing the required validation.

Ok thank you. I will subscribe on the issue.