Key-explanation

it still won't work

yes

I use the extension

Is this the one you were asking? 

While watching anime I noticed something, don't know if it got something to do with it. As the site loads the next episode, the player still remains from the previous...

So I can't use it in incognito mode?

Will it be fixed in the future?

Consider an anime that is not on your list. when watching that said anime malsync attomatically tracks and add it to the list as 'watching'.