I am not sure if this is related to autobid or more general. When you view the detail page of a player in the transfer list, you can see a list of the previous bids. Non-supporters can see only the last couple of bids. But still the buzzerbeater server sends a list of empty divs with class "hiddenBids" to non-supporters. Despite the fact that there divs have no text-content, they take some vertical space due to a 3px padding on their child div. This empty vertical space can accumulate in players with a lot of bids. I suspect that these divs are sent to the client unintentionally.
I am not sure how to attach an image here, but if you navigate to a TL player, you can see that there is a lot of empty space associated with these divs. Tested on the latest versions of chrome and firefox.
If you still want to add them to the document, they should have display:hidden by default, so that they do not take any space in the document flow. For supporters, these should be display:hidden by default, unless the supporter clicks on the "show all bids" button.