Failure saving blueprint after renaming component variable - engine transient

Attempting to save a blueprint that makes use of a component whose variable has just been renamed fails due to the following error.

Can't save [asset path].uasset: Graph is linked to private object(s) in an external package.
External Object(s):
/Engine/Transient

Try to find the chain of references to that object (may take some time)?

Pressing OK on the above message still results in a failure until saving is skipped.

Found on //UE4/Dev-Blueprints CL-3098294
Not a regression from 4.12.5 Binary CL-3039270

This occurs in Main @ 3098262

1. Open UE4Editor.exe QAGAME
2. Create a new actor component blueprint
3. Open it, add a variable to it named "TestVar"
4. Compile and save the actor component blueprint.
5. Create a new blueprint based on actor; open it.
6. Add the previously created actor component to it
7. Drag a GET of the component in to the event graph
8. Drag off of the Get's out, and place a SET TestVar
9. Connect the Exec of Begin Play to the Set node.
10. Compile and save the actor blueprint.
11. Open the actor component blueprint, and rename TestVar to 'Renamed'
12. Compile and save the actor component blueprint
13. Open the actor blueprint, and, without compiling, save.

Result: Failure to save
Workaround: Compile, then save.