Sonar RXP Crackles with multiple instances

I was trying to use multiple instances of RXP and after I add the second, the system starts to crackle, only on those tracks, even with freezing and bouncing.  Running version 8.5.3 64 bit.

could be a number of things..

the loops and their timings are out..

rex lib to playback is still 32bit.. if your using sonar 64 in win 64.. then it has to use bitbridge as a layer.. how do you get on with sonar 32 and the same thing?

what about your asio setup ? you assigning enough buffers..

with certain rx2's ... if you  mess with the timing too much of the chop points are rubbish, then that will come out when you play back regardless of the sound card etc setup