Items stay in cart forever

Hi everyone, as the title says the items stay in cart forever. This is a recent issue, it was working fine a few months ago but I am not sure when it started to happen.
I set the “Keep in cart” option for 1 hour but the items do not go back to stock automatically if the purchase is not completed. I tried 2 hours but it doesn’t do anything. Even after days have passed the items are still in cart, making them unavailable for other customers. Is there a way to fix that?
I use the Strapvert theme.