Thanks everyone for the responses!
I did fire up the helix yesterday - updated to 3.15, factory rest and restored from backup. Then added a couple of presets which were shared by a friend.
The next time I started the helix (a day later) it said something on the lines of “resetting the presets” and then the count went from 1 to a big number (not sure how much)
restarted it a couple of times after that as well - but now boots up immediately.
any clue why the reset happened again?