Can we see an example of the API responses sent by your private Forge instance? I suspect one of the pagination fields is "false" when it should be "null".
with the URI of your local Forge mirror and desired output file path substituted.
It sounds like the maintainer of that gem could make an update to return the correct pagination values, we are also looking into making the module tool more tolerant of unexpected values in the API response in a future Puppet release.