Howdy - lurk here often, but haven't posted until now...
I've been having this issue for some time now, but never sweated it much until learning how to perform ILS approaches. I'll take off, level off as per ATC, set the autopilot and switch it on. Eventually, I'll receive a new instruction from ATC and change the autopilot accordingly. I never have a problem with my heading, but the altitude response varies. Sometimes it'll climb/descend to what I specify, and sometimes it'll keep going. Am I missing something ridiculously obvious? This happens regardless of what plane I'm flying, by the way.
Thanks, all
Trainee
Chief Captain
First Officer