It seems like that is known issue, can you download that patch file from this thread https://stackideas.com/forums/code-in-posts-when-i-press-enter-to-change-line#reply-441401 and see how it goes.

I applied the patch and it does solve the issue.
Still, new line + empty line creates in the cose 2 <br> tags, which result in a pretty big space, wouldn't it be better if new line + empty line would wrap the text inside a <p> tag instead?
The resulting blank space would be smaller. Maybe I am wrong, but I remember those empty spaces being smaller before the latest update.

Thank you

Actually that is correct standard for the bbcode editor, if you enter 2 times mean it will add 2 < br > tags.

I also tested this on the those bbcode online testing tool, you can check my attached screenshot below.