Hi,
I'm afraid that's nothing to do with this module. You've probably only noticed this problem after installing Back In Stock Notifications but the problem was there already.
BISN doesn't affect any manufacturer-related functionality of Zen Cart at all!
Try posting a new thread in the forum with a much more detailed explanation of what you are doing and what you expect to happen and hopefully someone can help you!
All the best...
Conor
Ceon
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