Hey Wayne, I'm glad to see this post because it prompted me to ask about a recent problem I've had with broken animations that maybe you can help me with. In my case the problem occurred after changing the directory of my character rig from its original one. When I opened the anim file and pointed the broken links to the new directory, the animation is restored to the rig but the mesh no longer moved along with it. Any idea what might be happening there and how I could fix it? The work around I used was to delete the character, re-link it to the scene, recreate the rig proxy and then reapply the action.
Hi Kurt,
Excellent question.
I'll have to do a video but to fix the broken library link it is essentially the same way.
However, DO NOT SAVE THE BROKEN FILE OVER THE TOP OF ITSELF.
That step is very important!!!haha
Here's what you do. (in Blender 2.79, haven't checked in 2.8 yet)
Open the broken file > Save As (increment the number. ie anim_02 becomes anim_03)
Then in the outliner, change it to show the data
Down the bottom there will be a broken library link.
Click in there and change the name or location of the rig.
Save over the newest version ( anim_03 or whatever you just recreated)
Then reload that file.
It should relink everything on opening it up again.
I don't think I have encountered the problem with the mesh not working anymore, maybe you made it local or something? Don't know sorry.
Hello Wayne,
Sorry to intrude on this conversation but it's the only question that I've found which is similar to my problem...
Like kjcummings, I opened a file of my Rivet Animation but the Character was missing in the scene (see on the picture)
A potential solution that I found was to go in : File - External Data - Report/Find Missing Files
Save the scene and open it again... I tried but I think I broke the Rig...
When I do this technique, I can see my character again but the mesh doesn't follow the rig anymore and make weird stuffs... 
Do you have a solution ? Pleeeeeeaaaaaaase...
Thanks in advance and sorry for my english...