.The autoflight system is basic but robust. and does what it says on the tin.
Yeah, there is no 'mysterious' (and complicated) software here doing strange things surprising pilots. The basic approach modes, the autopilot functions are well understood (or should be) by pilots. If a pilot feels automation is doing weird things (sometimes VNAV can do it during complicated step-downs) he ought to disconnect it. I don't know if it was even legal by aircraft/autopilot limitations or airline SOP to have the autopilot engaged below MDA. In my own much smaller aircraft I am prohibited from using autopilot below certain altitudes for precision/non-precision approaches.