Maybe you have a REALLY slow LFO modulating?
 
Is this your own patch or one of the factory presets? If the latter, somebody else with Z3ta+2 could check if it's the patch. (Not me, though. I don't have it.)

It's the factory patch, "classic content/textures/constantly moving (hold"
 

bitflipper
Maybe you have a REALLY slow LFO modulating?

There undoubtedly are slow-moving LFOs... I don't see why they would act differently on bounce, or create that kind of offset though. 
 

I have a track on a project that has weird WAV rendering anomalies. I used Audio Snap to correct a few timing issues on a live conga track and after bouncing to clips a section of the track looked like I used a brick wall limiter to boost the volume up as high as possible. It shows solid blue for a few measures. Later in the same track the conga hits appear to be badly offset, yet when I play the track it sounds fine; no volume change or misplaced conga hits. I just assume that the rendering got wonky in spots, but the audio didn't get affected. I haven't tried to correct it, or even figure out what happened since it sounds fine. This is with SonarX3. It sure looks funny. 

Sounds are not always symmetrical in terms of their waveforms. Brass and wind recordings (for example) often look like this. It's not necessarily wrong, in any meaningful sense. How does it sound?

Something is up worth asking CW about.
 
I just loaded that patch (had to search for it, since it came up in "z3ta+ Classic Content -> Textures -> constantly moving (hold ), ran 30 bars of it (single note), and bounced the track. The wave form I got is what I expect to see.
 
Z3ta+2 was inserted as a simple instrument track when I did it. No DC offset issues in the bounced wave form.
 
Edit: I bounced it a few more times with different settings (64 bit Engine on/off) and still saw no DC offset issues. Z3ta+2 has so much variability in the generation of that wave that each bounce was noticeably different (which is sort of scary in a way).