Final Words

An important thing to remember is that GTA 5 games don't break randomly. Generally speaking they break due to user error or after a Rockstar Update. We have zero control over Rockstar, but we can control our modding.

If your game suddenly breaks for no apparent reason, look to the last mod or mods you installed, the last file or files you edited in OpenIV,  or changes to your Windows environment. They will likely point to the culprits. Always follow mod or script installation instructions carefully and double check how you've installed. So many forum posts swear that the mods were installed properly but on further investigation, you guessed it, there was user error.

Beware of bad advice. Be wary of morons on YouTube who claim 100% fixes for GTA5 crashes. Particularly the ones advising you wrongly to replace dinput8.dll with the one from the Windows system32 folder. It won't load any mods, giving you a false impression game is fixed. 

Reinstalling

Reinstalling is generally a total waste of time. Error messages will often lead you to the wrong conclusion that game files are corrupted - that's almost never the case. If you suspect issues with vanilla game files, do a Verify Integrity. It is much faster and is generally all it takes to fix your game.

Keep the reinstall only when everything else has failed and you've run out of options.

You may also want to read When All Else Fails - No Fix Works! at our sister site.