Flap asymmetric malfunction very unlikely on the basic Cessna aircraft and would only be caused by gross failure of the maintenance of the aircraft. The only failure that is likely to be undetectable at maintenance inspection is an electrical failure of the flap motor
The incident quoted above about a C152 giving uncommanded flap movment is unlikely to be a microswitch misalignment as such but a Malfunction of the flap position feedback cable that mis-positions the microswitch block to cause the uncomanded movment.