Checking back to confirm that re-doing the House of Hope area "fixed" the problem. Which is to say, I can travel back and forth between Wyrm's Rock and Lower City now. No idea if it's possible to recover the original save, but at least I didn't lose too much progress doing this.
I sent my save file in the support ticket when the problem is occurring, so hopefully someone will take a look for the sake of others who don't have this option.
