Not so long ago I overhoned my Friodur. Backhoning did not do the job, a coarser hone neither. What really did the trick is stropping it a couple of strokes with the spine lifted a few millimeters (about 1/8") off the leather followed by 10-20 passes on an Escher.

Stropping with the spine off the leather also works well on a razor that needs honing again (adds one or two shaves worth to the bevel).