I add to this myself, in order to help being helped:

I realised that said problem described above, ONLY happens in desktop view. It does NOT happens in mobile view...

In desktop, I have my website header (nothing to do with the forum) in a way that when opening the page, the header shows at a given height in order to show the website logo at a good size etc, and then as the viewer stars scrolling, the header gets way less taller to a size just enough to keep showing the sites navigation menu/links....

COULD the problem described be due to this fact? (I think so)

And if so, is this something could be sort at the forums end?, perhaps with some sort of css code or something like it?

Or should I get in touch with Divi Theme (my WordPress plugin builder) to see if they can sort this at their end?

Thanks once again? 🙂

Okay here its me answering to myself again 🤣 

I think this is now sorted, but Im not sure. Could someone please confirm?

Here is the new link 🤣 

https://mundopiano.es/foro-de-piano/foro-bienvenido/

From there all you need to do its to press in any of the topics (preferibly in the one with more answers as it makes "the issue" more noticeable.

Could be that what Im thinking that its a "wrong behaviour" its just normal because the forum its asked to work in a way that need to take viewers to the last post hence "the bouncing"

Or even considering the above statement, still maybe bouncing too much?

Thanks and again, so sorry bother you guys so much!