The following is from tech support on this point.
Yes the differences seen when looking at the wave shape, amplitude and bias for OSC 3 are normal for a Voyager, and exists on all models. The reasons for the slight difference(often noted as a slight difference in timbre to trained ears) is due to the differences in design for OSC 3 vs the other oscillators. The fact that OSC 3 has a Low Frequency Mode and is wired for direct modulation of the frequency of OSC 1 is what causes these subtle differences.
Hmm, well I guess I can chalk that up as a win and bragging point for me. See mom, all those years as a starving Audio Engineer paid off. I can detect subtle variations in the Oscillators of a minimoog voyager!
Thanks for the info. It wasn’t bothering me enough to bother tech support. Now, to get the filter to open up all the way letting that nice buzziness shine on!
Resurrecting an old thread, because I just spent the better part of the evening with my 4 month old XL trying to figure out why the triangle on Osc 3 was sounding ever so slightly different than 1 & 2. I am VERY grateful for all of the work the posters in this thread did last year to get to the bottom of this - and am quite happy having a very slightly different Osc 3 that works “as designed”. 
I think it’s because it’s a slightly different oscillator.
osc 3 drops into sub audio range the other two do not
Hi there, I just bought a second hand Voyager in mint condition yesterday. and immediately noticed that Oscillator 3 sounds a little different than 1 and 2. Especially the triangle wave sounds as if there is still a little bit of saw mixed in. Sounds a bit like the mixed Triangle/Saw wave (or “sharktooth”) in my Minimoog Model D.
Another thing I heard: if I set all 3 Oscillators to a pure sawtooth, Oscillator 1 and 2’s output are a bit louder than Oscillator 3 is. If I turn Osc 3’s volume all the way up, and 1 and 2 to approx. 70%, their volume is the same… Is this normal?
My Voyager is version 3.5.
It does sound different, I easily noticed it and tech support confirmed. Since I have calibrated several units, I can tell you it is true for every Voyager