I did get a few complaints of people getting multiple copies, and I see some duplicate listings in the logs, so perhaps there's something to test.
I've tried external bounce management products, one for 3.7, and the EZ one, which is supposed to work in 3.7, but is listed in the 3.6 folder.
Neither works, really. The latter is mostly non-functional, and the coder isn't responding to my post on the subject. The former is being distributed mostly unsupported.
Can you possibly build that feature into your product? I think it's the missing link, and the other options are failures.
Peace,
Gene