CDJ1000 looping problem

Hi

I picked up a second hand CDJ1000 (mk1).

What a great bit of kit. It works great and I am slowly teaching myself all the functions.

 There seems to be a problem with looping however. It only lets me capture a second or two and automatically stops the loop if I leave it too long.

 Do I need to flush the memory or something? Or is it possible there are some corrupt memory chips? Can they be replaced?

 Appreciate any advice.

Thanks