You are right, it's wrong. It is this tts voice issue. On ivona.con website when you choose Maja voice (it's duolingo one) and type in "Kot" it's pronounced wrong. But when you type "Kot a nie kod" it's pronounced ok.
Ouch. I remember that we used to have this bug... if it came back, we'd need some screenshots to prove it to the developers. If you had a chance to provide a screenshot for that, that would be really helpful.