When the Launch URL blueprint node is used to open a link on an iOS device, any question marks in the URL are converted to %3F instead and invalidate the link. This is different from the behavior on Windows and Android, where the question mark stays intact.
Please note: The device needs to be connected to the internet, even if the link isn't a real link, to see this behavior. It also does not seem to be device specific.
This also occurred in 4.12.5
Head over to the existingAnswerHub thread and let us know what's up.