Pressing F2 doesn't work when another key is being pushed. This means I can't join in as player 2 while I'm running/moving with player 1, and it makes a few tricks impossible to do. It works just fine when no other key is being pushed. What could be the problem?

You cannot call in on keyboard when pressing any keys, this is something that any keyboard player has to adjust for - you can look at any keyboard player's run to see how they do certain tricks, and it will be covered in the upcoming tutorial. It's something you'll have to just get used to but it basically becomes second nature to any keyboard player.

Oh I see, thank you for the reply!