DDJ400 is lagging very often while mixing, video link in desctiption.

Guys Hello.

I can't upload a video here so I used a streamable.com website 

https://streamable.com/i3zagc 

Take a look on video and somebody please help, didn't have that problem previously and now when I start mixing this problem occurs, what can I do? how can I help it? why I have that problem?

Also white RCA input has a little bit problem while sticking a cable.

P.S there is no official store of Pioneer in my country

I bought new Rokit 5 speakers I thought it was because of speakers, but it is still lagging.