wrote:

There was an accident here in Canada that resulted in a Canadian
AD forcing modification of the stops. A student and instructor were
killed when the rudder locked hard over when entering a practice spin
and they couldn't stop the rotation, thereby preventing spin recovery.

That was already posted on this thread. However, that aircraft had lots
of unrepaired and mismaintenance with regard to the tail that exacerbated
the problem. Still getting back to the original assertion, had they not
been in a spin already when it locked up, it probably wouldn't have been
an issue.