Doing more testing this evening and found another issue. I initially had the payment gateway set up to go to the PayPal sandbox. Tonight I disabled it after entering my banking info and PayPal address as the only two options. Upon attempting to pay the invoice, I first noticed there was no other option than for PayPal (there was nothing notating a bank transfer option.) Upon proceeding to PayPal, I ended up in their sandbox again despite it not being enabled (PayPal is set up as the default.) I logged out of that account and went back in as an administrator to double-check and, sure enough, I have only bank transfer and PayPal as payment options with PayPal as the default and sandbox totally disabled. I enabled GD Booster and cleared the cache, disabled it again and logged back in as a customer, created another dummy listing and went through the process again only to end up in the sandbox.
I’ll post admin credentials separately for someone to take a look at it.