Infinite Spinner is a bug on the Amazon Vine program that - as its name may suggest - shows a spinner that spins infinitely in its effort to populate the page with product details. However, this is a futile process that lasts indefinitely as it is technically a 'broken' feature of Amazon Vine currently. This issue is also not region-specific, meaning it can affect Amazon Vine members from all countries.
Ultraviner bypasses all infinite spinner issues because UV creates a brand new vine experience and does not rely on Amazon Vine original interface. The interface was created with this bug in mind from the ground up and it bypasses all the possible spinning issues.