So it's a bilingual channel and they just switch languages like it's no big deal?
Yes, and that's normal. I hear that young Czech kids are experiencing some issues understanding Slovak, but not adult Czechs. Been done that way for decades, both during the times of Czechoslovakia, and after the break-up. For example, English Premiership footbal games also used to have a combo of Czech & Slovak announcers (on the Czech Nova Sport TV channel) in recent years.
it sounds to me like a not a not very professional thing to do.
It's perfectly normal, I assure you. However, I would prefer only Slovak announcers for
Slovan's games. Only Czech announcers for Lev's games also make sense. But if it's a "neutral" game for us, say SKA vs. Dynamo Moscow, a combo of Czech & Slovak announcer seems perfectly fine and
reasonable, considering the channel has subscribers in both countries.
A funny experiment (that went wrong!) was made by Nova TV in the Czech Rep a few years ago, for a football 2010 South Africa World Cup qualifier. There was this
crucial game between Czech Rep and Slovakia in Prague, and Nova TV was so foolish as to call a
Slovak announcer to announce the game along with a Czech announcer on the exclusively
Czech channel. So, whenever Slovaks scored, the Slovak announcer was loudly celebrating on
Czech TV.
Many Czech football fans were furious. Slovaks won that game in Prague 2-1, they eventually advanced to South Africa (and among the top 16 there), while Czechs did not.
For two recent Slovan away games, KHL.ru was offering the official webcast, but Sport 2 was not showing the game. So, buying a KHL.ru subscription is a better option than buying the Sport 2 subscription. I'll be cancelling my Sport 1, Sport 2 subscription later this month.
First bring all Slovan games, then I can renew my subscription. 
