Since a few hours ago discovered upload of art fails constantly. This is the message shown after submitting html form:

<?xml version='1.0' encoding='UTF-8'?>
<Error><Code>SlowDown</Code><Message>Please reduce your request rate.</Message><Resource /><RequestId>130e557d-b53d-47f6-8d20-86e87b5a3788</RequestId></Error>

RequestId is different everytime. This problem doesn't exist about 2-3 days ago.