Has anyone had an issue with the exhaust fan on the P2 stop working?

While it sounds like the fan is in operation, it no longer vents like it used to.  I have about a 4' run of exhaust pipe connected from the machine to an external vent in my garage.  I used to be able to see the smoke flow from inside to the venting grate at the back left.  The venting was more than adequate.  I no longer see that and the machine fills up with smoke and smoke leaks out the gaps everywhere.

I've cleaned the fan, putting everything back properly, but still no proper venting.

Is there a way to test the fan without the machine powered on or running?  Can I get a replacement fan somewhere.