In browser preview of uploaded attachments broken with Fabric Editor

Summary

When attachments like Office files or PDFs have been attached to a page, the user can click on these files to have a preview of the file contents load in the browser. The first time a user opens such a preview it will take Confluence a few seconds to display the preview. The text "Your preview is on its way!" is displayed at this time. Generating this first preview typically took a few seconds at most, on Confluence Cloud before the introduction of the Fabric Editor. Now it takes between minutes and "forever" to generate a preview.

Environment

Fabric Editor

Steps to Reproduce

1. Create a page in Fabric Editor and add at least one attachment (drag and drop to page)
2. Save the page and open in view mode
3. Click on the attached file to open preview
4. Wait...

Expected Results

A preview of the attached file is displayed in the browser window

Actual Results

The progress indicator spins forever, or at best it takes x minutes for the preview to load. Most users will have given up long before it loads.

Workaround

• Restarting the browser will fix the problem (Chrome and Mozilla Firefox)