i've had that happen a few times i have the latest Firmware & everything is up to date,i was changing both presets & snap shots with Midi,i stopped changing presets with Midi & im just changing snapshots with Midi & it happened to me exactly the same way when i stepped on a preset button,what i had to do is make sure all my presets are backed up,which it will do this even if it's locked up then do a factory restore,you can do this by turning off Helix,then holding down buttons 5 & 6 on the front of the Helix Rack & turning it on it will do a Factory restore,it'll take a couple of minutes,after it reboots re install your presets it works for me & it has happened a few times,i talked to Line 6 about it & they said it was probably a defective preset but i think it's a glitch with the software,good luck