The two that come to mind are:
1) The 'continue' button on the page is now useless. It can never be pressed because by the time you reach for it after typing the last number of your pin it is already submitting and may even be on the next page.
2) If the user typos the last character of their PIN or types it then decides they want a different one. The typo one feels valid even though some typos go unnoticed, other times you hit a key and immediately realize you hit the wrong one.
If we want to continue with this, we need to change the flow to allow for 'forgot pin' on the confirm pin page.
I removed the auto submission, so this is all sorta moot.