My control tablet, an ASUS, also stopped opening pdf files after the 536 build. It shows them, but when you click on one, it doesn’t open, no matter how long you wait. Still works fine on the host machine, Windows 10 (3.8gHz Intel 7, 16 mB RAM). I use no streaming services. I have spent a lot of time creating and organizing pdfs and hope this excellent feature can be fixed.