When you view an old version of a page, the parameter &oldid= is added to the page URL.
If on a wiki without page forms a user hits "edit", then the old content is displayed in the edit window and when the user hits "save" the old version of the page just shown is saved again (and is now the current version).
When using pag forms, the formedit action ignores any "oldid" parameter, thus loading the content of the current version of the page in the form.
This is misleading for users who are looking at an old version of a page and click on formedit.
So PageForms should take into consideration that an &oldid parameter might be present on the page where the action=formedit happens and then load the correct (old) content to the form.