Hey I found this thread by searching because I had the same problem, however I randomly found out an easy fix while reading it that doesn’t involve changing codecs.
So here’s a still from a clip I recorded with PICVIDEO MJPEG:

Here it is imported into vegas normally (the problem we had):

To fix this you need to go into your 64-bit codec config found in
C:Program Files (x86)Pegasus ImagingPICVideoV4.0UtilitiesCodecConfigx.exe(default install)
And tick “Force YUV Output”

(also untick enabling interlaced when above a certain resolution, but I think that’s something to do before recording)
Now when you import it into Vegas, the color banding is gone but it’s really bright:

So add the effect “Sony Brightness and Contrast” to the master video bus and make the Contrast 0.125 leaving the other two at default values and it’ll look normal again:

It looks slightly more blue but you could probably fix that with a bit of color correction if you really need to.