Did the new build only change the payment system in the app?
No, that dialog changed. It went from being a modal dialog to a non-modal dialog. So, I can’t think of any reason why opening it would be problematic. Like I mentioned before, I had tried this out on my colleagues Surface Pro, and I never saw the behavior you described in the first place with the app crashing, although the older version of the dialog did seem to be locking up the app. What sort of Windows 8.1 tablet are you using? Does it have a stylus as well, and if so, is the behavior the same with your finger and with the stylus?
