Challenge Mode: 5 Stars not triggering

I've achieved 5 stars in Challenge mode on level 1, and the task even went away on the right hand corner in the task or quest list. However, the Steam achievements are not triggering, and the star graphic still looks like it's at 4.9. The Galaxy map shows no Challenge mode completion graphic, and I don't have the 5 star challenge mode unlock object.

 I kept playing for a while, let the star rating come back down, and up to 5.. again, and again. It's just not triggering the completion for some reason.