How to split steering column harness/hamonica?

The signal light issue with my 78 Vette continues.  I have discovered since my last posting that the signal light works normally when the steering column is moved to the upper position, but goes out when the column is lowered into a driving position.  Manipulating/twisting the harmonica can get the signal and indicator light to return to operating normally on both sides of the harmonica.  I wanted to open up the hamonica to check the connections inside. I have tried splitting it by inserting a small screwdriver into the slot under the curved tab on the side of the black connector, and pulling the tab outward, which I assume is how the pieces snap together, but the two sides don't seem to want to separate from one another?  Is there something I'm missing here, or is it just stuck together?  Don't want to force and break anything.  Haven't split one of these connectors before.

Thanks.