Possible bug in rekordbox?

Hey everyone!

I'm really new to DJing. Like I got my Pioneer DDJ-400 like two weeks ago, and started practicing on it in the last few days. But I've run into some trouble already.

I don't think the controller is faulty, more like the software I'm using. The controller is brand new, hasn't been touched before. It has a warranty though. (Guaranty? Guarantee? Warrant? Safeguard? I have no idea which one is proper)

I downloaded Rekordbox (updated it to the freshest version just today) but I noticed something really interesting.

First off (which is the least problematic one): Sometimes, when I don't use the controller for like 2-3 hours, but it's still connected to the computer, when I enter Rekordbox and load a song to any decks there's no sound. The crossfader is perfectly centralized, the volume faders are at maximum, trim knobs are in the middle. Yet there's no sound. When I uplug-replug the controller, restart the software (once I had to restart the computer) everything was back to normal. Except for one thing, which is...

Secondly (which is much much MUCH more frustrating) the headphone cue buttons are weird. I know that if I press them, I should be hearing the song(s) on my headphones, which are connected directly to the controller. I do, but it's like the mixer is all around the player. Like I don't hear anything below 5kHz. And I can't do anything about it. I tried restartng the computer, the controller, reinstalling Rekordbox, but nothing. I know as a beginner I shouldn't worry too much about mixing, but it's insanely frustrating that I don't hear the lower ends of the song.

Last, but not least: Rekordbox tends to miscalculate BPMs. I know how to count BPM, and I've run a few tests on different websites as well and it (rekordbox) sometimes halves, or doubles the BPM of a song. Also, is there a way to increase tempo with the controller (for synchronising/beat matching (which term is correct here?)) without raising the pitch? It's really noteable even when i raise the tempo by 5.

Could you please help a beginner (especially with the last two)? I'm completely lost, as I have no one to turn to for help, other than the internet...