We've encountered a behaviour with EPiServer Forms which we are wondering if it is by design, a bug and if anyone else encountered it. What happens is that form elements ends up being shown to the end user even if the elements haven't been translated to the site language nor in any applicable fallback language. We encountered it on our own site and could reproduce it in a fresh Alloy-project with the most current version of EpiServer and EpiForms in particular.

EPiServer.Forms version: v4.18.0

How to reproduce:

1. Go into the edit view in CMS
2. Select site language (e.g. sv)
3. Create a new form
4. Create and add a input text field and a submit button to the form
5. Switch language (e.g. en)
6. Make sure that the language doesn't have fallback language set to the previous one
7. Translate the form container to the current language
8. Copy form elements from the previous language branch, do not translate these elements.
9. Publish
10. Drag form into an applicable content area and publish
11. View page in secondary langauge (e.g. sv)
12. Submit

Expected: 

Untranslated elements should not appear, form should be empty in this particular case.

Actual:

Elements appear, with texts from their master language, and if a user submits the form the associated values are not present in "Form Submissions" in edit mode.
In the log a variation of the following line appears for each untranslated element:

ERROR EPiServer.Forms.Core.Internal.DataSubmissionService: Element '120' not found or the Form has not been re-published after was changed.

Regards,
Johan