I thought so, but it didn't

So you still get the same console script errors with that change? Or are they different?

It's the same error, everytime I move the mouse anywhere on the site

Move the mouse? Really? You have not described that before. So how does this manifest itself? What are the actual visual signs?

The forum works fine apparently, the only thing missing is the window title (it shows the url)

That looks like it might be a tooltip conflict to me. Try this - In your SP theme templates folder (and hopefully you are using a child theme) find the spFunctions.php file. Change the use of the tooltips to false as described in the comment. See if that stops the script conflicts.

I'll try it later (I'm at work now)... and I'll create a child theme 

OK. But again - you can test it just by making the change in the full theme. If it stops the script conflict errors then you can go for the full fix.

I don't see anything to suggest that this might be the cause but if the WP theme does institute its own tooltip routines we would not be able to tell that and it may be the source of the conflict.

Looks like it's working after disabling the tooltips

https://www.subnoise.es/foro/

So - loading their own tooltips lib which is fighting with the one we supply. Again - the one we supply is the WordPress standard and supplied library. But keeping it turned off will, of course, solve the issue.