Help! Discounts being calculated incorrectly

I just received a report from a good samaritan customer saying that the 10% off coupon he used gave him more than a 10% discount.   I looked at the order and confirmed it, double checked the coupon to make sure it was set at 10% and then went back through several recent orders and found that it's been happening for some time!  The discount is only being calculated incorrectly when dealing with a discounted product bundle.  Here's an example where the customer used the 10% off code (no other coupon or promotion is being used) and a product bundle was involved:


ORDER DETAILS                                     UNIT PRICE     TOTAL
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In this case, it's almost 15% off the total, but that's not a constant - on other ones where it's incorrect it was upwards of a 16% or more off the total.

This is obviously a big problem so any help would be appreciated.  I can open a ticket if need be but figured I'd post here in case this had been encountered before.  I can confirm that the coupon code is working just fine for all orders that don't involve the bundle.  Thanks!

Thanks Hamish.  I just tried to open a ticket but looks like the process has changed, I logged in and then got the message "We were not able to locate any ProductCart License Keys associated with your Customer Account. If you believe that you are receiving this message in error, please contact us."    I didn't realize I was going to run into a whole new problem trying to open a ticket! Must not be my lucky day. :)  I sent an email in and I'm sure we'll get this resolved, thanks for the help as always...