Since the lever height is tied to the block does the block extend below the frame as well?  Both of those measurements should be of concern if it fit properly prior to sending it off.  Pop a primed case to see where the firing pin strike is. I recently had an issue with my ‘ratty’ action (may have been in a fire) where the lever did not meet touch the lower tang which caused the block to raise slightly when the lever was squeezed which caused the hammer to not manually cock. Lots of functions are tied together in a high wall action. 

Jack

If your action was working properly when you sent the lever in for case hardening and nothing else was changed then the lever moved/warped.  When the lever closes the breach block will reach its highest point just before the lever closes.  As the lever travels the last fraction of an inch to full close the block will lower slightly.  This is called camping over.  As a result, the firing in will at center just before camming over, then slightly above center, and finally, as the lever fully closes back to center if the connecting link is the perfect length.   

The tab on the lever should be dead flat.  I suspect the lever may have warped in two places.  The tab behind the ears of the lever and the lever bow.  Watch your breach block carefully when closing.  If you see the camming over warping is likely what happened.

I first tried filing the lever, but it was too hard. Ultimately it took 5 minutes using a Dremel with a stone to remove about .003" on the sides of the coffin shape just in front of the trigger. Everything dropped in place and the lever just touches the lower tang.