I think the only bug I’ve encountered, and this happened more than once, is when I’d ask an NPC to teach me something. If they agree, and I get the list of things they can teach, if at that point I cancel the game crashes. If I cancel while they’re in the process of teaching, no crash.
Also, if I ask for a cash reward if I finish their missions, most of the commands like guarding and teaching skills become 0 percent. On the other hand, if I give them items that exceed the amount of cash they have, teaching skills and guarding a position seems to become permanently 100 percent success.