Interesting but not surprising reading. This, too, from that report, Centaurus:
Many pilots reported rudder trim knobs sticking out of neutral after intentional activation. A knob with debris underneath or mechanical anomaly found later on some airplanes can keep driving trim after release, despite it being spring loaded to release.
Several reports show that even when the trim operates properly, the trim indicator can either remain centred or show an erroneous indication.
Fortunately in most cases the out of trim situation could have been and was controlled by rudder.
Also demonstrates why defects should be recorded and properly investigated. It seems that the normalised deviation of accepting rudder trim system defects was exposed by the incident.