Mathematically, such a thing could happen quite easily. Or something like a winning song that was second with the juries but 6th with the televote. This year's results certainly go in that direction.
Furthemore, I still don't see any reason why 5 people from my country should have the same say as our entire paying televote, especially when these people are not guaranteed to have any relevant musical experience whatsoever and they apparently can't even correctly fill their results in *. To me, all these things are a problem.
Either the jury should consist of 3-4 times more (musically knowledgeable) people, or they should only count as a 25%/33% of the final result (my favourite option), or they should just go altogether. The current situation is absolutely ridiculous though.
* also, the Czech jury isn't the only jury who made such a mistake