I have decided to keep a diary of my experience with troubleshooting here in this forum. I am doing this so I have something to look back at, but also to share with the community.
As one who mods, I am always making edits to files, replacing textures with ones I create, adding add-ons, ALWAYS tinkering around with edits to gameconfig, etc. Last night, I broke my game somehow, and spent about an hour and a half with some intense troubleshooting, before finally nailing down what the issue was.
So it starts with me making edits to loadouts, vehiclemodelsets, popgroups, vehiclelayouts, weaponscomponents, and replacing distantlight.dds, corona.dds, and the bokeh textures with ones I created for my own use. Then I fired up the game, and was greeted with a zlib call error - the worst crash you can have, as it always means having to at a minimum verify steam cache or worst yet, reinstalling the entire game itself. But why? I have been modding my game the day GTA V was released for the PC.
First thing to do, is remove my mods folder. BTW, it only contains the update folder as that is where all my modifications are stored, and the X64 folder which is where all my sound modifications are.
Removed mods folder, and the game loaded up quickly as expected. BTW, I have refused new DLC updates since version 1.944.1 online version 1.37 to keep DLC bloat down, and to escape the dreaded DLC limits that users face nowadays. As one who mods daily, I have learned to keep on my desktop a folder called "working modded update". In it I store my update folder that is heavily modded and working. This way, If something bad ever happens, I can replaced my current non-functioning one, with one I absolutely know does work. However, I wasn't on top of it, as that working modded update folder was about four months old, and I had done a considerable amount of modding since then. It would at least serve as a base to start from.
So I replaced my current update folder with last known working, and the game fires up. I then shut down the game, and added all mods since then, and as nervously expected, zlib call error again! WTF?!? I then started looking for clues. I had added some new attachments for some weapons in loadouts - did I add something that wasn't compatible by accident?I looked through the file, but found nothing that conflicted. I then started looking through all sub-folders looking for anything that might jump out at me. While in update/update/common/data/levels/gtav/weathers I noticed that several of the .xmls were zero Kbs! WTF? I opened each one up, and they were all blank! How? Sometimes OpenIV does some weird sh*t when moving stuff around and making edits. Thinking I found the culprit, I replaced them with the ones I had a back up of, making sure they all were displaying the proper file sizes. Shut down and fired up GTA V. Crash with zlib call error, Ugh.
Back to it, I decided to look at the custom textures I made in update/update/x64/textures. One of the files I made edits to was graphicspc.ytd - where the bokeh textures are stored. I attempted to open it, and OpenIV prompted me with a corrupt file message! This MUST be it! So I deleted it, replaced with the vanilla from x64a/textures. I then added in my bokeh textures, making sure to properly set compression and mip-maps before saving. Then I double-clicked it to ensure that it was not corrupt, and it opened without issue. Fired up the game, and this time, I was stuck in infinite-loading! Solved one problem, just to experience a new one.
Now, I am in deep-thinking mode. I leave OpenIV alone, and just sit there in front of my monitor thinking. What could still be wrong? Now when I added all my mods back in, I excluded adding my add-ons, because when troubleshooting, you add things back in, in small chunks. A few of those add-ons though were .ymaps like Forests of Chiliad, Forests of Senora, Beta Vegetation and Props, etc. That was my WOW-moment! I said to myself, how can the game load, when the save-file has all this new data in it such as all the trees, shrubs, props, etc? Quickly went to gta5-mods.com, and DL'd flavaone's completed save file, replacing my own. Fired up the game, and tah dah!
I have had many, many, problems over the last three years, but never had an issue I could not resolve by just patiently going through the troubleshooting process. Never had to reinstall nor verify steam cache, to overcome anything. Today, I will add all my add-ons back in, and then swap out the newly added save-file with my own again. I don't expect an issue at all, but If something fouls up, I will update my diary here. Hope my thoughts shared here, helps someone out there should they ever run into trouble.