I too use C1.
I believe this is strictly C1's issue, not really an issue but rather a design feature.
C1 was designed with pro photographers in mind working on many photos from a shoot.
It doesn't seem working on one or two edits was their intent.
My workaround has always been to move the file in question to its own folder and open it from there.
You could create a "temporary C1 folder" and just work out of it.
This is my understanding which is flawed by my huge lack of knowledge.