My experience with this issue and a possible way to fix your game.
Number 1 reason for spawn issues are .ytd files, specifically the ones, that directly affect the PLAYER character. The game will prioritize these textures over everything else.
Now, a lot of .ytd files posted on nexus (or anywhere else) for some reason are compiled of textures with a certain texture compression format (B8G8R8A8_UNORM). These textures are sometime x10times the size of the original ones.
I won't go into too much detail, but this is how you can try to fix this yourself.
1. Determine your most used PLAYER textures. For example: gun holster, gun belt, knife holster, spurs, hat, face, eyes etc.. These are the textures you want to focus on first.
2. Download CodeX 22 and check the textures compression formats inside these .ytd files (click on Details tab --> File format)
Look at file names: Albedo textures (_ab), Materials (_ma, _mb) Normalmaps (_nm).
Generally speaking they should look like this:
Albedo - BC7_UNORM_SRGB or BC1_UNORM_SRGB (half the size of BC7, almost no quality loss)
Material - BC3_UNORM
Normalmaps - BC1_UNORM
For example, If you see a normalmap being B8G8R8A8_UNORM, you want that to be BC1_UNORM to save memory. Same goes for other types. And I see no quality loss whatsoever. No idea why 90% of textures are save 10x the size.
3. Export the textures you need to optimize and open them with an editing tool. I use Paint.net to change texture compression format. Save with ctrl+s, choose the compression format (Linear = Unorm) or RGB for albedo.
Things to note. Often, when changing Albedos from B8G8R8A8 to BC7 or BC1 I have to use levels tool in Paint.net, and change it to 0.5 to fix the brightness/lighting of it.
You can also downscale some of them (ctrl+r, change the size), until the spawns come back.
For me, the ultimate way to test spawns, is checking if the passengers spawn inside Saint Denis trams. The moment I have passengers spawn inside EVERY SINGLE TRAM, everything comes back including TRAINS, ANIMALS, VEHICLES etc.. Also, the TRAIN should always spawn outside Valentine at sunrise. Open Rampage, change time to Sunrise (wait 5-10 sec in game), teleport to Valentine Gunsmith you should hear the train and can see it for yourself.
In other words, you want to save as much memory as possible by optimizing the most used textures in your game. Which are 100% the ones, that your characters wears or has. Even if the .ytd files themselves are no higher that 2mb it is still worth checking if you can make them smaller without quality loss ( and most of the times you can).