Switch working intermittently
This is symptomatic of a poor connection somewhere, or a bad-on-arrival fan.  I'd rewire the switches using the screw terminals as a first step (don't forget to hook the grounds up when you do), and if that does not cure it, I'd try Craig's troubleshooting suggestion of switching the fan and the light.  If the fan still acts up, then return the fan to wherever you bought it.  If the light acts up when switched with the fan, then I'd say it's a problem with a connection.