I did some thorough testing of this just now, and the bad behavior is consistently reproducible. 50 seconds is the magic number, if you hold your finger on a fader it will disengage after almost exactly 50 seconds. I made a quick video to demonstrate:
https://youtu.be/p8g72p04uTQ
If you watch the video you'll notice the red light next to the rec/automation button stops blinking around when the timer hits 50, and you can sort of see the fader wriggle away from my finger after that.