After cleaning up the edge last night with the shaptons I took it for another spin again this morning. Toe is now as sharp as the rest of the edge. I didn't notice the edge deteriorating during the shave the way it did yesterday, so I suspect that it may have had a minor wire edge yesterday. I'll keep track of this over the next few shaves, just in case there's some inherent problem with edge strength due to the thin honing angle.
I like way this razor handles. The combination of the thin spine and quarter grind makes it feel like a frameback, but it doesn't look ungainly like a frameback.