Media enconder gets slower over time

[Lucas22230036680q]

When I first open Media encoder and render a 30 seconds animation, it is taking only 4 minutes. But when I try to render again after a few minutes, after a small adjustment, it takes 12 minutes. And this becomes exponential, it can take up to 1 hour and 30 minutes for the exactly same animation.

I have no idea of what is causing this.