We finally figured out what was causing the before_process - DP-5 log errors. When configuring the BrainTree Payment Module in the Admin area of Zen Cart 1.5.4 the second to the last item to be inserted is the Merchant Account ID. When you first open up a BrainTree sandbox account you will be given a Merchant ID and a Merchant Account ID. We mistakenly inserted the Merchant Id instead of the Merchant Account ID in the Merchant Account ID text box during configuration.