Save your character state often to protect from crashes. Simply open the skill menu and click "Accept". This will save your character's experience and allow you to load from this point in the event of a crash.
The game might glitch in some live-with missions, where the objective NPC will become stuck behind a wall and thus cannot be targeted. He may appear briefly, but you will be unable to maintain a lock on him. Walk towards the wall and enter the /kneel action to see through the wall. You can then click and target the NPC to complete your mission objective.