@Joose Seems you've tried just about everything. One thing that has worked for me in the past has been updating my video drivers. If you have an Nvidia card you should be fine, if you have an AMD card their drivers are total crap. Nothing to lose by updating.

@1995SUBURBANS Not sure what you mean by file to modify. You would need to write a script assuming it is possible.

Have you verified the integrity of your steam files first?

@mcal9909 Good to know. Thanks. Will check it out.

Codewalker or OpenIV

@JohnFromGWN P.S. If anyone cares to share other docs, please post them here and I'll append the list above. That would really be appreciated.

Update: I redid the scenarios with both the Spy Actress and Michael and indeed many of the null animations were animated with Michael.
I also noticed that some scenarios behave differently at random. For example, Cheering comes in 2 forms. One with just clapping and the other with clapping and jumping for joy. Not sure how the game decides which one to show, but run them 10 times and you will get different outcomes each time (1 of 2 as far as I can tell).
Also, the same animations are not exactly the same for these 2 models.
For example, Michael sits with his legs wide open while Spy covers up by crossing her legs at the knees and/or ankles.
In jogging Michael wipes of sweat off his brow, Spy does not.

I was very surprised, and pleased today, when I realized that the documentation that is spread all over the web on SHVDN was right under my nose all this time. It's a friend who develops AAA games who chewed me out when I complained I couldn't find any docs for the object models. Even though he doesn't even use Visual Studio, he knew that if i stuck my cursor on any key word and hit F12, all the metadata would appear - including tooltips when you hover over the properties, methods, functions, etc.
Much more convenient and easier to understand than just using the intellisense feature of VS.
and more practical than the official docs which I also found today at:

https://nitanmarcel.github.io/shvdn-docs.github.io/index.html

Passing this on so hopefully other noobs can benefit.
So in summary, when you are in the .cs window, just stick your cursor in the middle of a keyword like world or scenario and hit F12. To return to .cs, click the x in the purple box at the top right of this new window that appeared.
And to kill 2 birds, here are some other useful links:
Native functions: https://alloc8or.re/gta5/nativedb/
Native functions: http://www.dev-c.com/nativedb/
crosire /scripthookvdotnet : https://github.com/crosire/scripthookvdotnet/tree/main/source/scripting_v2/GTA
Good resource for entities (pictures and hashes): http://test.raccoon72.ru/
Animation List: https://alexguirre.github.io/animations-list/
Ped Tasks: https://github.com/crosire/scripthookvdotnet/blob/main/source/scripting_v2/GTA/Entities/Peds/Tasks.cs

Screenshots below from Visual Studio 2019 just to illustrate you have almost everything you will need to interact with SHVDN - once reference is added to your project. You will have one page for every keyword, click and F12 and hover over with mouse if necessary. Of course you also have intellisense as a great tool.

Some updates:
Object Browser (ctrl + alt + J) in VS will allow you to view references including SHVDN. (thanks @mcal9909)
Meta data will also contain useful information for example on how scenarios change depending on character model and other conditions. (thanks @grateful_for_mods)
As an example for Meta data, check out Scenarios.meta. Path to file will depend on your installation, mine as an example:
P:\SteamLibrary\steamapps\common\Grand Theft Auto V\common.rpf\data\ai\scenarios.meta
(Use OpenIV to view this .xml file)

Top pic clicking on Class World. Bottom on Class Tasks.

@Jitnaught thank you. I think I can workaround this, would've been a nice to have.