That component didn't fail or cause anything else to fail, and nothing else caused that. That's just glue. It's always looked like that. Can't say I know what the problem is with the sound because I don't have the unit in front of me, but usually the problem is the soldering job. The more recent set of pictures doesn't look that bad though, so it's hard to say.
If you're getting a crunching sound out of the pot when you move it, it's dirty inside.