Attachment thumbnails disappear after uploading a new image

[Luiza Salim]

Hello,

I am experiencing a bug in Trello.

After uploading or pasting a new image into any card, all image attachments across the board stop displaying their thumbnail previews and are shown only as "PNG".

At the same time, the "Remove cover" option disappears from cards where the first attachment automatically became the cover.

If I refresh the page, all thumbnails appear normally again. However, as soon as I upload another image, the issue immediately returns.

I have already tested:

• Google Chrome
• Microsoft Edge
• Incognito mode
• The upload requests complete successfully (HTTP 200 in DevTools Network)

This seems to be a client-side rendering issue rather than an upload failure.

Could you please investigate?