I can answer the second part. If the hunter is at strength 1.9 that means it is at about 63 hit points at the start of the fight. So, fewer hits are required by the bear to actually kill it. This is having a big enough impact to drop the win rate from what would be a good odds fight at full health to a risky proposition. Fighting with injured units is just asking for situations like this. Main point: not a bug in any way.