Error Redirect fails when an existing ID in the redirect url

[Simon]

Hi
I've got a donation page and the onError Redirect URL is 'https://futureswithoutviolence.secure.force.com/fundError?id=a196g000000O6eCAAS'

However when the redirect happens the url is updated with ?err=[whatever error message]
resulting in an invalid url like
https://futureswithoutviolence.secur...0card%20number
instead of
https://futureswithoutviolence.secur...invalid%20card %20number


Did something change and it's no longer changing the ? to & if the redirectURL already contains a ?

[CnP.Support.AM]

Good day @Simon

Would you please share the SF OrgID and grant us login access to your instance so that we can review it?