Okaaaay, Living Legend bugs and crashing to desktop... I think I've found a permanent solution that's resolved my crashing issues now after a bit more digging around.
As far as I know, the problem is if you start your campaign as Loner and switch to another Faction while playing through the Living Legend questline, or if you have to force the quest to start, it causes some sort of conflict where the 'Actor' (You, the player) doesn't receive the right flags and therefor the quest chain queries whether or not you have this flag assigned, and since you don't it crashes.
You can fix this! I think my issue started because I begun my playthrough as Loner and switched to Duty during it. To fix it, you need to launch STALKER in Debug Mode, once in game hit 'F7' and '0' to open NPC Logic / Execute, and type the following under Function Execute.
db.actor:give_info_portion("living_legend_stalker")
Save your game, reload the save, and then try to initiate dialogue with whoever it is you're crashing with. In my case, it was Stitch, Sterlok and Rogue, they all seem to be behaving normally now with no crashing occurring, fingers crossed it's fixed for the entirety of the quest chain. So if you crash to desktop talking to Stitch, Sterlok or Rogue, run the command above and save / reload.