ckeditor: pointer goes to the beginning of a preset text when you press [ENTER]

I have a textarea with a text already pre-established. This textarea I have converted to BBCODE editor with CKEDITOR.

The point is that when I write in the middle of the text that the textarea already has, the cursor does not stop going to the beginning of the text. Especially happens when I press [ENTER].

Thank you very much in advance. Receive a warm greeting. Juan.