Can’t get to step 3 on Multistep Form

Hi there,
I have inserted a multi-step form with the short code on a page. When I click on the button I get to the second step to select the amount. But then when I have selected an amount and click on the button to get to the next step (inserting contact data), nothing happens.

It only works in Chrome Browser and Edge, but doesn’t work in Firefox and Brave.

Brave gives me an error “Incorrect use of <label for=FORM_ELEMENT>

Thanks for any hint