Currently, if a donor already is a Stripe customer with an existing Credit Card saved on file, a new recurring donation (and the subsequent renewals) with the Stripe + Plaid gateway will use the Credit Card on file at Stripe, instead of the bank account.
This is especially problematic because the fees for ACH are significantly lower, so it's popular for extremely large donations. on a $50,000 donation, 2.9% + $0.30 is $1450.30, whereas the fees with ACH are capped at $50.