I have a similar problem:
Droplets work fine except on two pages the [[droplet]] code is just not executed and [[dropletname]] is displayed on the output html.
This is not a droplet code problem as i have multiple droplets and neither of them is parsed.
There is also not a single error logged neither to the php.error file nor to the display.
The pages where it doesnt work, is a page with the form module and another page within the bakery modul when you put in your address to complete an order.
I am running WB 2.8.0 Final with the security patch. I have already patched the frontend.functions.
php with changeset #1269 (ticket #869) but that doesnt solve the problem.
Here are the pages where droplets are not working:
http://www.kuhlaendchen.de/pages/kontakt.php(this page uses only the form module)
http://www.kuhlaendchen.de/pages/publikationen/buechershop.php (you have to put something in the basket and go the checkout where you enter your address details to trigger the droplet problem).
(this page uses only the bakery module)
Cheers!