Problem With Saving Changes to Product in WHMCS

We are testing the manual creation of products for clients. Most of the clients we are working with right now are in person so we are setting up their client records through the admin panel and then creating a product for their client record manually in WHMCS. We've also got a lot of clients paying for their services via check.

In testing, I've noticed that if I make any changes to the client's product and they are hosting on our MU site that WHMCS wipes out a lot of their data. I've also noticed this happen if I just click 'save' on the product screen (see attached). Originally I thought this might be a problem with my configuration but then noticed it only happens on products that are controlled by the provisioning plugin (products that create sites through WHM are working fine). FYI - the provisioning plugin is talking to my WPMU install and is setting up the sites just fine. The problem presents itself when making changes to the product screen in WHMCS.

The problem originally presented itself because I was trying to mark the product to use the Mail In Payment gateway and then once I clicked save it zapped everything. Since I've pinpointed the problem to only products associated with the provisioning plugin, I'm hoping you can help. Do you have any thoughts on things I should check?