NOISE IN TRACKS DDJ-RB

Buongiorno,

Pc Dell Latitude E6420

Win 10 Pro – Ram 8Gb – i5-2540M cpu@2.60GHz – 64bit   x64

Recordbox 5.0.1 rev. 11765-12282-12283-x64

48,000 Hz sampling
Buffer 256 samples (5.3ms)
Blue Audio Drop Out line at 50% (first 10%). Without using tracks the line will continue to pulsate at 50%.
Problem: During dj set (about 4 hours) at least 3 times on tracks that have no problem I hear a noise lasting less than a second similar to the noise of a radio that searches for the frequency. At that moment people turn to look at me, perplexed ...
Help.