For our business, bills are created and each payment is tied to a bill.  Melio processed (2) duplicate payments and delivered double the funds to our vendor.  In Melio, these 2 payments are showing as "linked Payments"

I have said prior that overall we have had a good experience with Melio, but now that this has occurred I will be looking at other payment processing options and will be spending the morning verifying ALL payments that were sent out this week for any other errors!