The pronounciation of opiskeletteko is wrong at the moment by the way. Don't try to repeat it! Sounds like opiskeletko
Yes, the TTS seems to be struggling with some of the 2nd person plural forms of verbs. I'll remove the sound from this sentence, until we can come up with a solution. Please remember to use the flag to report anything odd. :)
does Duolingo have its own TTS system or use a 3rd party one?
The sound I hear here sounds just like the sound for Finnish in Google Translate.
Opiskeletko is the 2nd person singular. Opiskeletteko is the 2nd person plural. These are mixed, July 25th 2020.
The audio is still saying "opiskeletko" instead of "opiskeletteko". Reported
Opiskeletko instead of opiskelettko. Reported 01/10/20
Still the same issue 7/2021