Hello,
I have exactly the same problem, I have 5 preset that I can not use any more. I can not do anything with helix crash with black screen, it's like a dead zone in my setlist. I reinstalled the firmware 2.82 do a total reset, nothing changes, I used HX edit to save a preset and use the helix directly, it does not work. I can live with this dead zone but I'm afraid it will spread. My helix LT is no longer under warranty. I am French and it is difficult to communicate on English forums for me.