Koalas escaping???

Whyyyy are my koalas escaping through my glass barrier? As you can see at the end- there is a glass habitat barrier going all the way from the ground to the top, but they are just walking straight through it:) ive replaced the glass multiple times, moved the barrier etc but nothing seems to keep them in... Its way easier to see the glass in the daylight, but i swear it's there- just hard to see as i cought the video during night heh