Be careful when closing on exit
The electronic cat flap is supposed to stop the cat from going out using two pins that pop up behind the door. In this case, only one pin was coming up and my cat quickly figured out that by scratching at the door on that side, he might be able to get out.
So my advice: test the cat flap before you install it ;)
That said, Zooplus customer service immediately sent me a brand new one, which I was able to test and install to replace the faulty one. Thanks!