CDJ 2000NSX2 Loop problems

I have a pair of cdj 2000NSX2 for 3 years, only used at home.

In one of them a week ago, if I use the loop, for example at 4, and rather change to 8, the player makes a delay that it's enough to blow a mix.

The other player doesn't make that.

Sorry my english but I Hope someone can help me.