BBCode Editor not working when the reply is very long

Hello,
I noticed that when the reply to a topic is very long the bbcode editor is not working anymore.

Eg.

- the reply is so long that in order to apply a style or a link to some text I have to scroll back to the top to find the editor
- I select the text I want to be eg. bold
- I scroll to to the top of the window to find the editor tools
- I click on on the "Bold" button on the editor
- nothing happens

the same applies to inserting a url, image, and all other styles for the text

forum is here: https://accademiainfinita.it/forum

Thank you!