Rekordbox Performance Mode

I am having mega problems with the sound quality when using performance mode. I am using the latest version of the software and it crackles and pops when using the ASIO software which was fine before and I find this pretty convenient for playing back through my Pioneer DJM 750 mixer. I've tried everything, reducing and increasing the buffer rate, decreasing the master volume etc and nothing works. Having had numerous problems with the license doing it's own thing I've just about had it with this software, and this is vital for my gear as I've got 2 pioneer digital players which run off this software and it's driving me nuts.