Oh no! My guess is that it is device related, as well. I'm using a Roku to cast my Obe Fitness App for my workouts. It hasn't worked at all since the new update; however, the forced pin now works. I haven't checked every single app, but Obe has been the main one that didn't work for me (and the main one that I use to cast to my TV).
This really falls back on Apple, as this 'quick passcode fix' may only be temporary or app-specific.
They need to push an update to fix this bug (and focus on their QC, because they push out so many buggy updates that break things.. :( )
I would recommend that you use Screen Mirroring in the mean time. It's annoying and most of my apps don't support it (forcing me to use a browser instead of the app), but it does work...
Again, this is an Apple issue --- it appears to be a bug that is impacting some apps and devices and not others.
So sorry that this didn't work for you! Waiting with bated breath for Apple to fix this... .