So, this happended twice with me. I was on a managed climb and away from my system when the a/c reached crusise altitude. However, instead of holding it, the cruise altitude was surpassed and speed also was way higher than the curise speed.
Throttle was at climb detent; with manual intervention I got the aircraft to slow and climb down to a 1000ft below cruise altitude; barometric pressure was set to Std post FL100.
Even after that, the aircraft kept flying 1000ft below the cruise alt of FL340 and pushing the altitude knob for managed climb to FL340 had no effect. Any ideas will be useful.