Fantech FG4 inline fan got noisy

Hi;
One year ago I installed a Fantech FG4 inline fan in a return-air system that brings cool air back to my stove room.
I got some good advice here on controllers, and it worked well.
But, when I started it up again this fall, it was suddenly noisy, with a grinding/whine noise that was not present last year.

Any ideas what is going on? Could the fan have gotten dirty, or become imbalanced?
There is a high-pitched grinding whine, that oscillates a bit.

did you pull it apart and check for a mouse nest? my brother inlaws nabor went to start his boat this past spring and wound up going for a motor job. some how a mouse built a nest in one of the cylinders and when he started it all that stuff for the nest and the mouse herself made the motor throw a rod.