This patch is meant for Adyen_Payment extension extension compatibility:

Main conflicting issue is that "adyen_hpp" method inside this extension does not follow Magento 2 API for frontend payment methods and implements a set of "virtual" or "fake" payment method listings identified by brand_code instead of method_code and is missing some expected methods for Payment method objects

Solution is to patch following OneStepCheckout file:

[OneStepCheckout installation path]/view/frontend/web/js/payment.js and replace method "selectMethod"

with following method:

Replaced method adds conditions needed to detect payment methods by brand_code and also implement at least one expected method to its options.