Bitcrush Distortion on Playback after CPU Spikes

I’m currently running Cubase Pro 9.5.30 with a pretty large projects consisting of 60+ audio tracks, no VSTis, 64bit mixing, 32 bit recording at 88.2 khz on an iMac 5k, with High Sierra 10.13.6. In each project I’m primarily using Softube Console One with UAD integration, Hornet VU Meter MK3, FabFilter Pro-Q 2, Altiverb and Softube Tape on multiple tracks. I also have 8 seperate master outputs with my stems, feeding a Burl B32 summing mixer. The two Apollo interfaces I have listed in my signature are running in multi-unit cascade mode so I can have 16 outputs from my computer for the B32. The B32 goes into a Burl B2 A/D convertor which feeds back into my system via S/PDIF. The B2 also acts as master word clock for my whole system. I also have a UA 710-d unit connected through ADAT (but that’s only used for tracking, not mixing).

I’ve been getting bit crushing style distortion on some of my tracks and outputs (namely the ones feeding the second Apollo unit) after random CPU spikes during playback, usually if I’m doing something else in cubase at the same time. Otherwise the CPU meter runs about a third of the way during playback. No tracks are frozen, and I have multiple Folder tracks, Group and FX Tracks in all of these projects. No Vari Audio is being used.

Changing the buffer size makes the distortion go away but it comes back later after working on a project more (this happens with multiple projects in the same configuration). I’ve tried high and low buffer sizes and get the same results. I’ve also tried turning ASIO guard off and on, or at low, normal and high settings and still get the same results. I’ve turned airport off and have no background apps running besides the UAD console and control panel apps.

I’m currently trying to switch from Pro Tools 2018 to Cubase Pro as my main DAW so I’m still somewhat new to the program. I also do not experience any of these issues in Pro Tools or any other DAWS I own (Logic x, Ableton Live and Studio One).

Any ideas as to what could be going on here and how I could fix this? Thanks!

A friend of mine has the exact same problem on win 10. Even on projects that are super light. I’m curious to know the answer to this.