Hi all,
Every time I export this track, I get different results. Everything starts out fine - the results are perfect
(verified via null test) up until the automation curve brings up the wet level on an instance of BREVERB 2. Then, things get weird - BREVERB's output is uneven, with random jumps in level and quality. I've tried numerous exports but only a digital loopback provides predictable results.
Here's the track. Not much going on but two instances of Izotope Ozone and the aforementioned reverb.
[Yeah, this is a mastering session.] 
Here's the output on five different tries
(magnified). Everything is a perfect bit-for-bit match until the end, where the reverb comes in, and then you don't need a null test to see they're very different each time:
To clarify, the first is a 64-bit export to WAV. The second is the same, but exported in real time - it's better but not perfect. The third is a loopback, manually routing my Lynx card's digital output to digital input (24-bit) and appears to be ideal - looks and sounds great. The fourth and fifth are identical 24-bit fast exports to WAV, one right after the other - they're different!
Any ideas what may be causing this?