Song Stopped suddenly or changing the bpm (delay or something like this)

Hello there…

I have a problem… I had problems several times with djay during my last gigs… Before it has always functioned very well… During my sets suddenly a song stops, it seems, that there is something like a delay or I would say a changing in the bpm and sometimes it gies in then. I can’t fix the problem, perhaps someone has an idea:

Djay 4.2.2
OS X 10.9.3
1.3 Ghz Intel Core i5

Thx, Chris