I have a node type with an OG Entity Reference field tot the group (og_group_ref). This field is saved by Autosave. In the autosave_restore() the og_group_ref value is still available in the #form array. But after drupal_render($form) the og_group_ref value is gone. Strange thing is that in the html the surrounding form div for this element is present, but no form field inside.

Is this an autosave issue or a bug in drupal_render()?

The surrounding form div in the html:
<div class="field-type-entityreference field-name-og-group-ref field-widget-og-complex form-wrapper" id="edit-og-group-ref--2"></div>