Plugin interferes with PayPal Smart Button

I just noticed a problem when WP Fastest Cache is used with WooCommerce & WooCommerce PayPal Checkout Gateway.

The latter plugin can create PayPal Smart Buttons, which take the online shopper directly to PayPal. (Instead of being directed to the shopping cart).

However, when the WP Fastest Cache is activated, the PayPal popup screen tries to load for a few seconds, and then disappears.

Is there a way to prevent this from happening?

(To see the behavior, please click on the link. Choose a color option for the product, and then click the large yellow PayPal button.)

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