Hi,
could you please check directly in the database whether that field is present in the document type coupled data table (in this case it is the CONTENT_MenuItem table)?
Also, could you please go to Site Manager -> Development -> Document types -> edit your type -> Fields tab and just click OK button so the XML schema and form definition are refreshed?
Have you modified page menu item document type? Added custom fields or set inheritance? Unfortunately, there was a bug fixed in the hotfix 6.0.8 when similar issue appears in case document type inherited from some other document type.
It does not happen on all documents
Do you mean that some page menu item documents with teaser image are synchronized and some of them are not?
Best regards,
Ivana Tomanickova