Topic: Replacing a file can break the whole page
I have been uploading pdf's, putting them in my exposition, and then putting a custom thumbnail image.
(Choosing a preview image doesn't allow you to type in a name and search, unlike all other "add media" interfaces, btw)
The problem is that I have changed a thumbnail and uploaded a new one with the same name. To work around some clunkiness in the interface (I can't upload a new thumbnail in the "change preview image" interface) I went to a new editing window, deleted the old thumbnail and re-uploaded a new thumbnail in the media interface.
Back in the original editing window, in the "preview image" tab, I removed the old image, then chose the new image (which has the same name) and clicked "submit." I got blinking dots and then it never finished. I tried reloading the page and now it says "an unexpected error occurred" on both the edit and preview pages.
My whole page has disappeared!