Because I work at an airport and see the belt system you all have to know that there are broken locks all over the conveyor belts. I would always bring my bags inside to check them. The street drop at my airport has a huge drop off that connects to the main belt, it is not very gentle and the bags get caught and stuck if they are wheels down so they are beat up and then they get shot out of another machine, handled two more times after tsa and then two more times at the destination. That is why your suitcases look so bad sometimes.
It is rough on them and I see locks, tags, the medal pulls, etc all over the belts. Twist ties and zip locks are your best bet.