App is updated to support new firmware. If your using new app version with older firmware, there may be some compatibility issues with some features. Not saying this is your issue, but could be.
If your saying 3.2.5 works fine, then there is a bug somewhere. This doesn't sound like a reason...
So you used to be able to see a live view of the 4k front camera for the past year, but not now? Any component changes? New phone? Are you running the lasted app version? Have you plugged the card into a computer to see if you can see the files there?
Card are considered consumable product, so they definitely degrade. However, I’m thinking more that maybe the card your using is not suitable for use in the A129 Pro DUO.
What brand and model card is it?