When more than 20 Image-type assets are passed to a Thumbnails API that accepts Asset IDs, like /v1/batch or /v1/assets, the entire request errors with a “There are too many requested Ids.” error, even when passing less than the maximum number of IDs allowed for this endpoint.
This bug affects the Creator Dashboard - try going to https://create.roblox.com/dashboard/creations?activeTab=Image and resizing/zooming out your page large enough to show a lot of assets at once, then reload the page. None of the thumbnails will load, and this thumbnails request will repeatedly error:
This bug is especially bad because the only workaround is fetching the details of each asset manually to determine which are Image-type assets.
This limit is also nowhere to be found on the thumbnails API docs, which makes the thumbnails API no longer a valid replacement for the removed thumbnail endpoints:
Page URL: https://create.roblox.com/dashboard/creations?activeTab=Image