I've had yeast behave this way. It was using US-05. Only time it's ever happened, though I use that yeast all the time. It just clumped up like cheese curds, all the way through fermentation (you should have seen those globs churning around during active fermentation). When it was done, it dropped out, like normal. Beer was perfectly fine. If it gives you a hard time, just cold crash, and I'm sure those clumps will drop out.
On a less appetizing note, do an on-line search for "clumps of yeast" and see what you get. 'Almost ruined beer for me.... My wife's response: "Geez, I could have told you not to do that!"
Cheers!