I tried your vignette settings, but did not see any flickering.   Is the flickering evident in the final render or just on the timeline? Also, what are the soft-contrast effect settings and what are media / project details?

The flickering is present in both render and preview. Also, I have a whole chain of color correction plug-ins as well that maybe, combined with the Soft Contrast, causes the flickering. I'm not sure how to show you the effect chain though.

Here are the settings for the Effect tab:

Project settings:

Here are the copied media settings under General from one of the clips (the rest should all be the same):

General
  Name: S01E13.mp4
  Folder: C:\Users\User\Documents\Vidding\Reign
  Type: AVC
  Size: 959.61 MB (982,644,961 bytes)
  Created: Thursday, December 15, 2016, 1:12:23 AM
  Modified: Thursday, December 15, 2016, 1:27:33 AM
  Accessed: Thursday, December 15, 2016, 12:29:55 PM
  Attributes: Archive

Streams
  Video: 00:42:23.207, 23.976 fps progressive, 1280x720x12, AVC
  Audio: 00:42:23.232, 48,000 Hz, Stereo, AAC

ACID information
  ACID chunk: no
  Stretch chunk: no
  Stretch list: no
  Stretch info2: no
  Beat markers: no
  Detected beats: no

Other metadata
  Regions/markers: no
  Command markers: no

Media manager
  Media tags: no

Plug-In
  Name: compoundplug.dll
  Folder: C:\Program Files\Sony\Vegas Pro 13.0\FileIO Plug-Ins\compoundplug
  Format: AVC
  Version: Version 13.0 (Build 545) 64-bit
  Company: MAGIX Computer Products Intl. Co.

(Also a note: I just now updated to 545 build)

Sorry, no luck so far re-creating flicker from soft-contrast blur vignette.   Maybe someone else will chime in.

As a workaround for the blur vignette, you could instead try applying a gaussian blur with a feathered mask.

Do you apply the slow motion on the event clip you are applying Soft Contrast?

Sorry, no luck so far re-creating flicker from soft-contrast blur vignette.   Maybe someone else will chime in.

As a workaround for the blur vignette, you could instead try applying a gaussian blur with a feathered mask.

That's alright. Thank you for looking into it though, it means a lot! As for the workaround, I'm not really familiar with that method...I just tried it with cookie cutter, and it doesn't seem like it will work, also I'm not really sure how to create it with traditional mask. But using a mask on every clip I can see becoming pretty inconvenient anyway...I like to just be able to include everything in one effect chain. But thank you anyway for the suggestion!

Do you apply the slow motion on the event clip you are applying Soft Contrast?

No, it appears to do it whether there is Velocity effect applied or not.

If it helps, here are a couple of clips that have the flickering:

On the first one it's in the upper left corner, and for the second one it appears on the left from top to bottom.

I just observed that for the second clip that flickering only occurs if I add the pan/crop zoom out effect. If I take that off everything is smooth. Moving the pan/crop tab to the very end of the effect chain does the same thing, but not for the first clip.

It's all very strange. XD

Looks like it has trouble detecting the edges...

I had similar flicker issue on my last project starting at 3:52

But for this one, I had Color Curve and Soft Focus to 'soften' the Background. But need to experiment with this Soft Contrast.

Another wild guess :)  - do you have motion blur applied to that track?  Turn off make a difference?

Another wild guess :)  - do you have motion blur applied to that track?  Turn off make a difference?

Oh no I haven't had that turned on during this process. Lags the editing too much.

Just did an experiment: removed all other color correction, leaving only Soft Contrast, and the flickering is still visible.

I know this is an old topic but I've been having the same flickering issue with soft contrast. I didn't really get to the bottom of the issue but I found a way around it. Just remove soft contrast from each individual clip and add it to the video timeline instead. Hope this helps someone.