Cropped overlay video track appears for a microsecond only in rendered mp4 file, despite appearing in project preview window.
I am running the latest version of kdenlive as of this post, on Windows 11.

can't identify what "cropped overlay" effect/composition is...
i'm using latest Nightly build for Windows (11) every day and using transform effect and crop-scale-tilt i dont' have issues on rendered files.

Did you by accident change the length of the clip when the effect was already on it?

I've had simmular problem when i changed the clip length, and back at original. It seemed like the effect didn't correct itself at full, leaving one frame without it.
I repaired that by deleting that wrong effect and renew it again. Now i tend to never do that again, altering after effects.