[Andrei Stanescu]

Thanks for the help, your idea was better.
I managed to get it working. Apparently, the problem was rendering with the cpu. I changed it to cuda, and it worked. Not only that, the rendering was faster and everything seems more smooth as well.

[Andrei Stanescu]

I forgot to mention, I did try rendering without resampling and with smart sample, but no still no effect.
I did managed to get it to work, by creating a new project and adding a small video as a test, which worked fined.
Unfortunately, I’ve put around 5-6 hours into my original project, so I cannot start over just to add this effect.
Any other ideas what the problem might be?
Last option would be to render the video, open it in a new project and apply the effect from there.