C-182T G1000,KAP150 question

I've now had two run-away climbs with the KAP150 and wondering if
anyone else has seen this. In both situations I was established in the
climb with the 150 set to about 600 fpm with a higher altitude armed.
I'm not sure what I may have done that started the situation but it may
have been after I slightly reduced power for the climb. In both cases
the 150 started to bring the nose up slowly until we were at about 57
knots. I dialed the 150 down to about 200 fpm and the "trim in motion"
voice annunicator sounded. After holding Vx for about 2 minutes the
nose dropped and the plane resumed normal climb and eventually captured
the target altitude. Has anyone else had this issue with this
configuration? This would be disturbing in IMC if you weren't watching
the system closly. I wonder if the system somehow got itself on the
back side of the power curve, but I assume the software knows about
that.

-Robert