LG Dryer Overheats Senses Restricted Airflow Without Duct Attached

Last week my electric LG Clothes Dryer (Model DLEX2650W) would turn the drum, but it wouldn't heat up. I replaced the thermal fuse and high limit thermostat.  I cleaned lint out of the exhaust vent.  I cleaned lint out of the machine.  While cleaning lint out of the inside of the dryer I also found 42 plastic guitar picks. It ran fine for a week then had the same problem.  I ran the "flow sense" test on the dryer.  It indicated I had restricted airflow.  I disconnected the vent and ran the flow sense again, venting the air directly into my basement. Even without the vent attached, I got the 4 bars on my "flow sense" test, indicating severely restricted air flow. I opened up the dryer again to see if the blower wheel was obstructed by lint or guitar picks that I missed last time.  It's not.  It spins freely with no wobbling. I could probably replace the thermal fuse and high limit thermostat and run it for another week or two, but I would like to know the source of the restricted airflow. Any ideas?