All builds of version 21 have this error.
IMHO

The "GPU acceleration of video processing", is it on or off?

I get the same result when positioning by pan/crop in Vegas Pro 21; however, the issue does not occur if the events (using 9:16 still images) if the images are positioned using track motion.

The "GPU acceleration of video processing", is it on or off?

In both cases.

The "GPU acceleration of video processing", is it on or off?

Here, the color 'spread' occurs with GPU acceleration either on or off.

The "GPU acceleration of video processing", is it on or off?

Here, the color 'spread' occurs with GPU acceleration either on or off.

In both cases, this happens on version 21

have you try to move it Color Grading before Event Pan/Crop in Video FX Chain?

have you try to move it Color Grading before Event Pan/Crop in Video FX Chain?

A very good suggestion - that works.

All builds of version 21 have this error.
IMHO

@gorGaram Do you want it to colour the entire surface or just the image?

@Gid Of course, only the image. There should be no staining of the entire surface. For example, I have 4 pictures to a picture, and all are colored differently. They shouldn't paint each other.

have you try to move it Color Grading before Event Pan/Crop in Video FX Chain?

If you move it later (pan\crop), then "colored traces" remain.
I don't think that's a good solution.

If you move it later (pan\crop), then "colored traces" remain.

@gorGaram  ... could you please screenshot the 'CGP before Pan/Crop' that you are getting highlighted with an arrow or the like the color traces that you are seeing. Using the CGP before pan/crop, I'm not seeing any color traces in Preview to Best quality in the preview window.

have you try to move it Color Grading before Event Pan/Crop in Video FX Chain?

@gorGaram Works for me. I set the project up like yours.

& with two events, I've left a gap in the middle to show it isn't on the entire screen

If you move it later (pan\crop), then "colored traces" remain.

@gorGaram  ... could you please screenshot the 'CGP before Pan/Crop' that you are getting highlighted with an arrow or the like the color traces that you are seeing. Using the CGP before pan/crop, I'm not seeing any color traces in Preview to Best quality in the preview window.

Upper to the left, lower to the right, traces of painting are visible.

have you try to move it Color Grading before Event Pan/Crop in Video FX Chain?

@gorGaram Works for me. I set the project up like yours.

 

@Gid There are traces on your video too, only they are not bright.

@gorGaram I'd disagree, the colour picker would see anything that isn't white. I've tried a few effects with a picker.

@gorGaram said: "What am I doing wrong?"

Use Pan/Crop to select what you want to show on each track.

Use Track Motion to locate your selection on the screen.

Using the same frame sizes for both the Project Settings and media in pan/crop, I cannot repro that result with the CGP being placed before Pan/Crop.

Use Track Motion to locate your selection on the screen

Exaclty ... as I suggested earlier on in this thread.

@gorGaram said: "What am I doing wrong?"

Use Pan/Crop to select what you want to show on each track.

Use Track Motion to locate your selection on the screen.

 

@john_dennis In your project, the colored layer is at the bottom, of course it does not paint the top layer. Swap them.

Exaclty ... as I suggested earlier on in this thread.

This works, BUT it applies to the entire track, on which I may have several different clips that need their own settings. This leads to the fact that you need to make a new track for each clip. In version 20, it just works fine.

@gorGaram said: "Swap them."

Does this suit you?

This works, BUT it applies to the entire track, on which I may have several different clips that need their own settings.

True, but if you've only got several video events that need processing this way, the number of tracks used don't cost any more. On my timelines, I have lots of tracks dedicated to track motion for one video event only. To be fair, this would be a problem if there are dozens or hundreds of video events that need a separate video track for their unique positioning.

Referring to my last comment, this is what I got with the full timeline and then the two individual tracks solo by means of muting the other track:

Again, using the same frame sizes for both the Project Settings and media in pan/crop that you have shown in the original video.

@gorGaram said: "Swap them."

Does this suit you?

@john_dennis I'm probably wrong, you've got it done by track motion. I wrote about this above.