You do sound like you have had some unfortunate experiences, but there's a bit of detail lacking to make any comment on causes or frequency. The guarantee question has already been dealt with elsewhere, still honoured I understand.
I agree about your different definition of 'flyaway'. Change of flight mode from GPS to non-GPS assistance isn't a loss of control or any kind of 'flyaway' as such, it's a change in flight mode. A colloquial aviation term that might better suit some of the 'flyaways' here could be 'letting the aircraft get ahead of you' - so a flight mode or attempted manoeuvre where the pilot doesn't have the skill or capacity to carry out the actions, monitoring and corrections to achieve the aim. So say, steep turn (30 plus degrees) - OK. A steep approach - again, on it's own OK. Lining up on approach - OK. But attempting a landing by lining up on approach during a steep decent by executing a steep turn - for a less skilled pilot might, well result in 'the aircraft getting ahead of you'....in this case possibly a spiral dive. So a change of flight mode, during an autonomous flight close to a obstacle....higher chance of the aircraft getting ahead of you....depending on your skill and capacity of course
I have to say it never sounds good to have to admit 'the aircraft got ahead of you'...but personally, when talking to other pilots, it always sounds much better than blaming the aircraft for a pilot's own lapses.