If your Electrum wallet is 2-Factor (TrustedCoins), MPK will generate invalid (?) addresses and your customers will send the money to an unknown destinaton. I think this problem is related with 2-Factor Wallets, since TrustedWallets charges 0.0005 BTC / transaction. Little orders will never arrive you, because this fee. I tried with a normal - standard Electrum wallet, and everything was working. Maybe a ISSUE with TrustCoin wallets? Maybe a developer backdoor to send funds to his own wallets? Don't know, still waiting a reply from Developer.