DJM 250mk2 combinated with Controller DDJ 400

Hello! 

I recently bought the Pioneer DJM 250mk2 to use it as a mixer for my turntables. I also had 2 Serato vinyls, so I started using Rekordbox DVS in relative mode till I can buy the Rekordbox vinyls. I find the mixer amazing, great sound. I also bought the controller DDJ 400  a few weeks ago, and, while I was using DVS, and because I can't afford to buy a DDJ XP1 yet (that's my first idea) I tried connecting the DDJ 400 to use the beat fx, pads, etc. To my surprise, Rekordbox recognised it and, without having to change a single item in the configuration, I started to use the two of them together. The problem is that when I do that, the tracks start to sound like a little bit "broken". I'm sure that changing something in the configuration I can use them without trouble but I can't find what's the problem. Thanks and greetings from Argentina!

Santiago