Popup over Paypal window

Hey guys
when i want to checkout with paypal and click on Paypal, there is always an empty popup shown above the actual paypal window.

you can move it to the side or close it to complete the Paypal login.

This seems to be in every browser i've tested.

Do you have an idea, how to fix this?

Example Page:
https://localsbodensee.de/shop

Greets,
Sebastian

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