They all try to escape. You should be worried if he actually can. They are just exploring. Glass is not natural to them so they keep trying to get across the invisibile object.
Not much you can do.. but keep it inside.
It is not particularly a sign of stress. How big is the enclosure?
Add rocks and things in it, which it can climb and amuse itself with. Doing this you will also artificially enlarge the walkable ground area (by adding layers it can walk on).
