I'm having the same problem, and have a case open with Autodesk support. @Mike_Hurtado has been on it.
What I've found that I THINK might be the culprit is "phantom" alignments get created when you add a feature line as a baseline. They aren't visibile, they don't show up in toolspace, but they are selectable with the Select All command. Those alignments seem to exist in the same site as the feature line it's based on, which I think is what's causing the funky interaction with the feature lines. You may be able to see them if you run the command for a new surface profile.
I have a quasi-fix that is a nuclear option, and probably not recommended. But it's the only way I could clean up my drawing enough that I could get my feature lines to take elevations again. For me and my complex drawing, this was better than totally starting over.
1. Delete any corridor baselines that reference feature lines.
2. Make a new layer (I called mine ALIGN-BAD)
3. Freeze the layer your normal alignments are in, then do a Ctrl-A (Select All), you will probably find multiple alignments in your properties window. Change their layer to the ALIGN-BAD layer.
4. Freeze all drawing layers except ALIGN-BAD. Select All again, then erase. Purge/Audit
5. Use some other method for grading off of your feature lines. Hope that Autodesk comes back with better recommendations soon. If you're positive that you're done making changes to the geometry or elevations of the feature line, it MIGHT be safe to add them back. I THINK they're safe if you don't change them. It's only when I've started changing things that the weird behavior kicks in.