This mission has been bugged for years now.
Yes, they repaired the arrow cart, thank the Gods, but one lethal bug is still on:
When you die during the mission and respawn, Kas and Jory are suddenly back in Fort Salma, leaving you unprotected (no Mesmer shield) to the Modrem Thrasher boss, which makes the fight (and staying alive) a lot harder.
It’s not undoable, but it’s still a pain in the behind. It would be nice to see this fixed.