upload widget with dontpush is flakey

I am trying to use Upload in immediate mode, with dontpush. More often than not, if I upload a file, within a second or two of completion, the Upload textfield and upload button will appear. Refreshing the page makes it go away. If you don’t do a refresh, when you do something else an error message of the form…

…appears in the console. This occurs a high percentage of times in Firefox, IE and Chrome, whether via localhost or remote.

Has anyone else seen this? Any fix or workaround?