Thanks for your response.
The screen record was helpful. It turned out to be related to the first event on the timeline (which I didn't try) . Even after deleting envelope points, the default point at timecode 0 is never deleted by Vegas. This resulted in a duplicate when copying the '0' envelope point, with as a result the error. I have updated the files on Github.

@marcel-gielen, there HAS to be a 'default' point with the default value. When adding points, I always check to see if a point already exists at that time and, if it does, change the value - otherwise add a new point there. For example:

        public void AddVelocityPoint(Envelope VelEnv, Timecode PointLoc, double PointSpeed)
        {
            EnvelopePoint a = VelEnv.Points.GetPointAtX(PointLoc);
            if (a == null)
            {
                a = new EnvelopePoint(PointLoc, PointSpeed);
                VelEnv.Points.Add(a);
            }
            else
            {
                a.Y = PointSpeed;
            }
        }

@marcel-gielen Unfortunately I still get the same message.

@jetdv Have you considered making a script that removes silence, or at least removes the absence of voice. In this chrome extension example it plays at a faster speed where there is no speech, but as a Vegas script I'd like it to remove the non voice completely

@Former user, look at the series that just finished:

And then combine that with the series that just started:

You'd definitely need some modifications to also remove the video when the audio was removed so that the "empty" areas went across all tracks but, otherwise, I believe this is basically what you're asking for.

@joelsonforte.br I fixed a couple of issues. One of them was the handling of destination tracks which did not have a volume envelope. This was most likely what you experienced.

@jetdv I purposely did not check for duplicates, since I first deleted all points within the event area. Later found out that Vegas does not delete the '0' point 😞
No a real good programming practice imho, after a 'list clear' the list is probably not empty.
 

removes silence, or at least removes the absence of voice

@Todd-A0, have you considered the option of using a noise gate?

@marcel-gielen Now works fine here. This script will be very useful.Thanks!

@juan_rios From what I understand @Former user wants a script that identifies the silences present in an audio file and allows their removal, similar to Vegasaur Silence Detector tool.

@marcel-gielen I was looking for a script that does what Joelson shows(and what Jetdv is developing), didn't know Vegasaur had it. Within Vegas like that is exactly what's needed, so each cut can be perfected if required, Excessive jump cuts can be annoying but more accepted in short form social media edits, and some cuts can be hidden with optical flow seamless transitions.

@juan_rios From what I understand @Former user wants a script that identifies the silences present in an audio file and allows their removal, similar to Vegasaur Silence Detector tool.

 

Ah! Sorry. My English is very basic and I didn't understand well.

@marcel-gielen Now works fine here. This script will be very useful.Thanks!

@juan_rios From what I understand @Former user wants a script that identifies the silences present in an audio file and allows their removal, similar to Vegasaur Silence Detector tool.

 

I would like to have a script that removes the silence I cannot afford to buy vegasaur.

That's what I listed up above...