Sorry about that - the Jaksta for Mac is not able to record properly from Deezer at the moment. It looks like they have some kind of protection to stop programs like Jaksta. We will look into this and add support for it in the future if we can.
When I record from Deezer, the mp3 file that is generated is not good. The audio is all cut and defectuous. Still I can detect that it's the same music, but with lots of audio defects on the way.