CKE not saving properly when editing content with iframes and text below

Steps to reproduce:

1. Paste this velocity code inside a page:

{{velocity}}
#* Your velocity code here *#

{{html clean=false}}
<iframe></iframe>
{{/html}}

{{/velocity}}

1. Edit the page(press E)
2. Add text below the iframe
3. Save the changes
4. Edit the page (press E)
5. Click Save

Expected results:
The text is saved.

Actual result:

The text is deleted.

Workaround:

Remove the clean=false property.