I have found:
If the trap has bar doors that helps to make the otter or animal to stay off the wire.
The animal will work the largest openings first.
I believe one of the reasons guillotine doors work so well is that they move, rattle, and are strong. The movement and slots make him want to work the door more so than other parts of the cage. If you have to release one in most cases a sliding door saves the chance of a bitten finger.
That was one of the reasons for coming up with a trap that has a swing down door on one end and a guillotine door on the other. They tend to work the guillotine door more than the swing down door. You can also still stick one end up in hole and still have the benefits of a swing down door.
Whatever an otter eats is run through him in about 4 hours. So he is going to get pretty yancey, pretty quick.