I have used V-vocal successfully for years, but recently I noticed a very obvious flange sounding distortion on parts of the vocal track, wherever I apply pitch correction, even for very slight changes in pitch.  This distortion is very obvious and cannot be corrected by formant changes.  Any ideas on what is wrong and how to correct it?    I am using X1 Producer.   Thanks.
 
Greg 

Are these artefacts on the S, CH, T sounds etc? If so it's because these are white noise and have no tone. It's a pain but what I do is split my vocal clips so that those sounds are not included in my selection when I make a V-Vocal clip. Those parts of the track therefore are not processed. It was like a lightbulb turning on for me when I discovered this and my V-Vocal pitch correction has been flawless and flangeless ever since.

I know this is extra work but it can have the extra spin off of allowing you move your V-vocal clips to another track leaving just these sibilant sounds on the original track so you can use the volume fader subtly as a de-esser.

Hi soffmeister, the flange artifacts are not on the S, CH and T (sibilant) sounds, but on the vowel sounds.  In fact, this distortion also appears on part of the V-vocal clip where I never even edited the sound!  For example, if I make the slightest pitch correction to one small part of the V-vocal clip, the entire clip becomes "contaminated" and you can hear this flange distortion on other parts of the clip, here and there, which I never touched.  When I later bounce to clips, the flange distortion remains.

Indeed, V-Vocal is a messy tool.  It looks like a vocal editing suite, but in reality you have to slice your vocal up rather thin to get acceptable results.
 
If you experience "the flange" on a vowel, it's possible that V-Vocal did not automatically mute the original clip (behind it!).  I've seen this bug many times.  Or a clip in another take is not muted.  Either way, when a slightly off-pitch line plays with a corrected on-pitch line, it gets flangey by nature.
 
I hope this is your issue, because it's an easy fix :)
 
P.S. Band name:  Flangey By Nature

Thanks Studious but the problem is not an unmuted clip behind it.  However, I did some more testing and discovered that this flanging distortion varies on the same part if I play it back over and over again.  For example, sometime I will hear the distortion on that part, sometimes no distortion, sometime a lot of distortion, sometimes barely noticeable distortion.  This makes me think the problem has to do with audio settings or my sound card.  Any suggestions?  I am using ASIO drivers, 10 ms buffer size with Focusrite Scarlet 8i6 interface.  Thanks.

similar thread http://forum.cakewalk.com/FindPost/1815653 with some possible causes

Ah yes, if your vocal is not super clean, it can lead to the problem you describe.  This includes any headphone bleed, room reflection, other noise in the vocal recording...

I think scook's link to "V-Vocal Strange Phasing Sound" may have my solution, as explained by bitflipper.  I had intentionally recorded these tracks with my mouth very close to the mic (to get a strong proximity effect) but that is probably messing up V-vocal.  I will re-record further away from mic to see if that solves the problem. 
 
Thanks forum members!!
 
Greg