Problem with Serato and my Denon DN HC 4500 controller.

At first everything was just ok, and suddenly the play button on the left deck on my denon DNHC 4500 started to malfunction, till there was no more play.

It was as if you were using the stutter...... weird. but if you stop pressing the play button, the track would go back to the cue point.

So I took the denon to the store to see what was going on. I thought it was the denon for sure.
After a couple of days the tec people told me that nothing was going on with the denon, since they tested it with a bunch of dj softwares and everything worked just fine.
They suggested that perhaps it was my serato.
I`m working with ver 2.1.1 and I´m about to download the newest version.

What do you all think of this ?????