Gavril D-Series messed up

You should use the tool for finding broken mods

 

There are some common files and some specific for each car. Mod files have priority, anything can be overwritten. It's against the rules to overwrite files unless there is no other way to make something work (which nowadays is probably never the case). This rule is heavily enforced on the repository and any mod that overwrites any file gets rejected (as far as the moderation can check). But third party websites don't care about this rule and commonly overwrite a lot of stuff, causing things to become increasingly more and more broken with each game update with that mod installed.

 

Almost. Each vehicle only takes files from its own folders and from the common folder (it's hardcoded), unless the vehicle's materials reference textures in other locations. The priority for the game loading the files is: first from vanilla game, then from all mods in an unspecified order and each new one overrides the previous, then lastly from your userfolder. Cache is an entirely different thing. The cache for vanilla vehicles is not dynamically generated but the devs add it manually to the game after each update and hotfix to speed up loading. This doesn't fully work for mods though and may produce unpredictable results in rare cases, so the mods cache is dynamically generated. However if a mod has cache already in its structure, then it will have priority over the dynamically generated one, which is part of the reason why some mods can't be fixed by clearing cache. Mod cache can also conflict with vanilla game one if it's in the structure, so a mod part can break the whole vehicle when installed, and when a mod overrides a vanilla part and has such broken cache, you can have really weird issues that are hard to troubleshoot because even the game doesn't know what is wrong. There are also other things a mod can generate that are not cache but get deleted after clearing cache. It can be cooked textures converted from png to dds by the game (modders are supposed to include the dds variants in the mod already to speed up the process, but not all do it since dds takes more file size, although it improves performance when using the mod), or temporary materials for modders to use when they haven't created a material for a mesh. These are temporary things that you are supposed to fix before publishing the mod, but it's easy to forget. When your mesh has temporary materials, and in the next update of the mod they get used by something, it won't work for other users because they will still have the temporary ones, so they must clear cache after updating the mod or else it won't work, it's a really common problem. But the game won't generate temporary materials for things that override vanilla content, so the end user will just get a no material error instead when a vanilla material gets removed and a mod overrides the vehicle part with an old version that still uses that material. Same thing with textures. This is an extremely common issue on bootleg mods, because the authors don't even care if their mods break the game like this, neither does the moderation of the websites they put their mods on. If it was here it would never get approved. Statistically from what I've heard for every 1 or 2 mods that get approved on the repo there is 1 rejected one, and the most common reason is overriding vanilla files, it's ridiculous how many people don't care that their mods break the game.