I noticed this problem using the LPF both in djay for Mac and in djay2. It sounds like clipping when you use it (at around 1/2 to 3/4 of the LPF level). It is stronger in some songs and parts of tracks than in others, but it’s definitely a problem. LPF in Traktor 2.6 and Traktor DJ works clean without crackle or clipping sounds. I can also send a recorded audio sample if you like.