It seems like a problem about the package @truffle/hdwallet-provider, maybe the problem is the line 13: privateKeys.split(','), according to its doc, if you want to pass an array of private keys, I think you should use like following:
const privateKeys = [
"75xx45",
"85xx45",
];
//start at address_index 0 and load both addresses
provider = new HDWalletProvider(privateKeys, "http://localhost:8545", 0, 2);