Have been testing it quite a bit, and it's actually stocks with a greater negative than -10%. That seems to be when the bug kicks in. So it's not necessarily only the highest faller (but clearly always worth doing the highest).
Stocks between -10% and 0, you just get your exact money back you spent.
I'm not sure. I tried it on the worst 'random stock' in my game which is Animal Ark (-70% or something at the start of the game and it was -26% just now when I tried it), which is enough to make it the 2nd worst stock... So I tried Lifeinvader, and also AnimalArk at -26% and also Vangelico which is now only -14% but only Lifeinvader worked... I bought and resold the other 2 stocks twice and both times, no big profit... I think actually I made like +5% or something because I did make a tiny bit of money but it was definitely below 5% because I invested like 1.2 million in them each time and it was still 1.2 million.. but I think it did go up like 20k or something. But definitely didn't go up 500% or something.
Not saying you're wrong. But for me at least, in the scenario I described above with Trevor after By The Book, definitely only Lifeinvader (the #1 worst stock) worked and the #2 and #2 worst stocks (also both worse than -10%) didn't work.
Yesterday when I tried to instantly buy and sell Lifeinvader though, it didn't work either. I had to switch characters (hence the switching in the video). It never worked when I just bought and sold. But 1 mission later, it did... I'm not sure why.
It clearly can work but maybe there are odd cases where it can't. Just like, why does it sometimes give you 500% return and others 800% return... My guess is maybe it's related to the crash amount? So, if LIF says -50%, you get +500%? -80% = +800%? not sure... there seems to be variance though. i tested it 15 times before that video and my returns were about 600% 9 or 10 times, 900% a few times, and I even got just 10% return once (it didn't work). So it seems like it can vary.
http://youtu.be/bs2X9CFC_lM
Man, the sharing feature on PS4 is perfect for this game
Haha yeah this is basically the perfect type of game for it... open world where the fun comes from the random and unexpected.
Even not to actually "share"... I'm using the Share feature to document my game file for than anything. I'm trying to make a perfect story file, and I want to take pics, record videos, etc of all the choices I made, how all my missions were (time of day, weather, clothing, random conversations, etc)... what vehicles I chose, what random events happened, what 'roleplays' I came up with for story missions and what new stories did I make from random events...
It's so easy to record all that stuff now. Snapmatic sadly has a 96 picture limit so I'm happy I can use the PS4 now to take shots or record vids. Probably 1 of my most favorite new parts of GTA V on PS4 (alongside the new traffic variety and first person).