Sorry for the late response, this post got missed in the list.
Internal server error is a general undisclosed error. To be able to assist you, please provide the actual error log entry which you may find following the debug documentation.
I get the same error periodically. I'll dig into debug. But the request for me is more this.
When I am uploading a number of images, sometimes an individual image will error out. I would like to be able to click on the Warning sign and retry the image.