The problem is that PayPal will not always allow changes to the default funding source. And even though it states that PayPal will use the backup source if there are insufficient funds, that is not what really happens. Instead, my bank account gets dinged a $35 fee for insufficient funds and the account goes into default! That is not making me happy... If I had known that PayPal would not use my backup source, I would have planned ahead, but instead I trusted PayPal and now have a hassle with my bank account.
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