RT field duplicates on web

I added a RT field in the middle of the HTML code in a form. When i open the form using the web, the field’s contents display in the place where i added the field and at the botton of the page. In the code, the field is not called anymore bellow the place i added it.If the field has some image, it only displays at the botton of the page.

Is it a bug?

Has anyone know something about it?

Thanks in advance!

Renata