DOMException: Blocked a frame with origin…

Al finalizar la compra, tanto en el modo de testing como en producción, en la consola estoy viendo un error de CORS:

DOMException: Blocked a frame with origin “https://sandbox.mercadopago.com.ar” from accessing a cross-origin frame.
at h.<anonymous> (https://http2.mlstatic.com/frontend-assets/px-checkout-frontend/3569.477c6459.js:2:2348)
at Ui (https://http2.mlstatic.com/frontend-assets/px-checkout-frontend/app.17a73193.js:2:785588)
at _l (https://http2.mlstatic.com/frontend-assets/px-checkout-frontend/app.17a73193.js:2:833137)
at El (https://http2.mlstatic.com/frontend-assets/px-checkout-frontend/app.17a73193.js:2:832707)
at bl (https://http2.mlstatic.com/frontend-assets/px-checkout-frontend/app.17a73193.js:2:832245)
at https://http2.mlstatic.com/frontend-assets/px-checkout-frontend/app.17a73193.js:2:844029
at Su (https://http2.mlstatic.com/frontend-assets/px-checkout-frontend/app.17a73193.js:2:844540)
at uu (https://http2.mlstatic.com/frontend-assets/px-checkout-frontend/app.17a73193.js:2:838296)
at Ko (https://http2.mlstatic.com/frontend-assets/px-checkout-frontend/app.17a73193.js:2:778996)
at ru (https://http2.mlstatic.com/frontend-assets/px-checkout-frontend/app.17a73193.js:2:835190)

La compra no se termina de realizar.
Esto es en Chrome, pero pasa también en Firefox y otros browsers.

Hay alguna configuración errónea de mi lado?

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