It gets worse. The retaining nut can be seen hooked over a piece of paper. The threaded portion of the nut cracked and separated from the rest of the nut. Before long the fuse will not stay in place, no matter what.
Step 1: The insides
Step 2: A simple solution to restore the converter
Step 3: Solder a hook to the fuse
If you are concerned about blowing a fuse and not having a replacement, get a second fuse and solder a piece of hooked copper wire to it, too.