Really interesting. I know this Thread is a year old, but right now i have exactly the same Problem.
Flashforge Finder, using the Flashforge Software and PLA.

I have also tried a lot and found that when printing complex structures the print misses out complete slices, so my models looking the same as yours on the Pictures.
The Fails are always in the same height, so i was quite sure that this is not a Problem with the PLA or the temperature.
Simple forms like a pillar work fine with no Problems. So what you suggest is that the Support may be the Problem. That would make sense as the pillar is so simple that it does not have any Support.

I will try in this direction and give an update.