I think I've fixed this by ensuring that the rescued Damsel is NOT a hero. It likely plugged some random number into the hero status of the Damsel, and didn't know how to deal with the outcome! Thank you very much for finding this!
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Confirmed, this is fixed. If the damsel had an unusual hero number (which could happen if nothing was assigned) all bets were off in terms of the experience gain you can get from them. I've fixed it everywhere random damsels can be generated and put in an extra catch to treat them as non-heroes if their hero value is out of the ordinary.