Hi,

I guess the video is 1-4 frames shorter than the source video. And you start playing the source video with the same trigger which starts recording and you stop both of them with the same logic or when the video ends. Like this:

Note that I start playing the Video Player with the restart pin, which resets any previous play time.

And you do everything in the same frame rate and not in Realtime recording:

Then both videos should have the same amount of frames.

I noticed that you connected an output pin to an input pin of the same module:

This can lead to all sorts of problems, so I would advise against it. There is Looping pin in the Video Player module, you should probably turn that off instead of the above logic.
However, this is likely not the source of your issue.

I would suggest doing some tests where you simplify things, like connecting your source video's video pin to the video recorder. This could give us some clues if things go wrong in your Flow Editor logic. Also first you should try to reproduce the problem with a few minute-long video, if it happens with short videos, then it is very likely that something is wrong in the Flow Editor logic.

Also, which version of Aximmetry were you using to render the videos? Note that since Aximmetry version 2023.2.0 the input and output timing system were revamped, which might have caused or fixed this issue.

If you have lots of repeating compounds or modules, you can probably simplify things with Linked compounds: https://aximmetry.com/learn/virtual-production-workflow/preparation-of-the-production-environment-phase-i/scripting-in-aximmetry/flow-editor/compound/#linked-compound 
Or in some cases with Array compounds: https://aximmetry.com/learn/virtual-production-workflow/preparation-of-the-production-environment-phase-i/scripting-in-aximmetry/flow-editor/compound/#array-compound

Warmest regards,