Problem with preview_open_now (www/preview_buttons.zpt)

Dear developers

Silva 1.5 offers the possibility to publish documents from the public preview. Unfortunately this doesn't work in our installation.
The situation is as follows:
I've created a document 'myDoc' in our ETH root (ETH is a special object extending Silva Publication). In public preview, therefore, the URL is 'http://localhost:8084/silva/ETH/myDoc/preview_html'. If I click the 'publish now' button, I get the error message 'The object at http://localhost:8084/silva/ETH/edit/preview_open_now has an empty or missing docstring.' Obviously, the system doesn't find the script 'views/edit/VersionedContent/preview_open_now.py'. Looking at the url displayed in the error message, I see no 'myDoc' appearing there. In fact, if I call http://localhost:8084/silva/ETH/myDoc/edit/preview_open_now, the document is published as expected.

I can solve this problem by patching the page template 'www/preview_buttons.zpt'. If I replace in '<input class="executor publish" ...' the attribute 'name="edit/preview_open_now:method"' by 'tal:attributes="name string:${here/id}/edit/preview_open_now:method"' all works fine.

However, I don't like to patch Silva. And in fact, if I publish Silva Documents in plain Silva, there's no problem. It seems that our layout infrastructure interferes in a problematic way with the Silva framework.

Any ideas why calling 'edit/preview_open_now' works when the document is in plain Silva and leads to failure when the document is in our layout?

Regards,
Benno Luthiger