I can only think these problems are server based. I did several Episode 1 chapters on Legendary last night; they were flagged with the symbol and complete on the timeline, but today three of them still say I only completed them on normal. I started Episode 2, Chapter 1 on Heroic - half way through the game did it's 'let's reset your skills and loadouts to SR1' trick, but I finished the level anyway - it showed as complete, but when I boot back up two hours later there's no record of it or the challenges at all. Each time this happens, and in Multiplayer, I get less and less urge to come back. Fighting through levels on Legendary solo isn't something I want to do over and over just because the server didn't remember I'd done it.