There is a bug in the Hidden Input Form Component.
The component appears to allow multiple input definitions, but in fact does not. Only a single instance of a given key / value pair is allowed.
If there are multiple "name" / "value" pairs defined for a form, you can only input a single "pair" per Hidden Input Component.
Thank you for reporting this! As far as I can tell, you are trying to add key/value pairs from the Attributes panel. When you do it that way, they are added as attributes to the <input type="hidden"> element. When submitting a form, browsers send only the name attribute and the rest are ignored. You will need multiple hidden inputs to pass your data.