This is a weird one.
Shield Model: P2571
Shield Version: 6.3 (24.32.406.472)
Remote Model: P2575, P2920
Plex Version: 184.108.40.20671 (0bedfc04)
Plex Server Version: 220.127.116.1173
I have the Shield remote that has the headphone jack with the rechargeable battery. I can 100% duplicate this error by scrolling through On Deck on the plex home screen 1-3 times. It will crash.
If I use my TV remote (via CEC) it does not crash. It only crashes when I hold the button to scroll, if I tap it, it is fine.
I notice the remote (while holding down a button to scroll) scrolls VERY quickly. The TV (CEC) remote scrolls 1/3~1/4 the speed. My best guess is Plex is just getting overloaded and crashing. This is the remote that came with my Shield, and it only effects Plex, the other apps I have on the Shield handle the faster scrolling fine.