Not sure why or HOW that happened
Automatics are no different to any other bit of gadgetry in that they are subject to
(a) design protocols - the end user needs to use them as the designer intended.
(b) error trapping and tolerance - does the gadgetry have a reasonable capability to recognise things which aren't quite right ? .. either internal or external to the gadget
(c) operator incompetence (in the technical sense .. ie not knowing enough about how to operate the system)
(d) database errors - the system and the operator might both do the right thing but the source database creates a GIGO result
That is to say, to trust gadgetry without suspicion is done at one's peril.
So far as the end undesirable outcome is concerned, such things occur when the pilot is not on the ball. The automatics help the operator do whatever it is he/she is seeking to do ... but they do need to be watched closely in case they do something a tad strange .. which they are wont to do at times.
If it ain't working like you want it to ... then do something different. In general, that involves reverting to a lower level of automatics involvement. That, in turn, might involve anything from pressing a button which the pilot hadn't intended pressing right through to pressing the big "OFF" button and flying it like a real aeroplane.