I was preparing a post and had just attached a zip file. Just thereafter the following appeared. It is attached to the page and scrolls with the text. The three dots scroll like a progress bar. Now the post can't be edited or anything else (Preview, etc.)

Any way to get rid of this?
Note - the zipped file was a FreeCAD FCStd file. When I attempted to attach it to the post, a forum message said, "File not allowed" so I zipped it. Why not add FCStd files to the list of allowed files?
Thanks,
Don C.
Comments
I've added the .FCStd extension to files allowed for attachments.