Why you need to backup before updating.
There are quite a few posts, past and present, regarding GTA5 updates and what you need to backup, but very few on the reasoning behind it.
The reason is simple, ScriptHookV.dll, the file which makes modding possible for most of us, needs to be updated with every GTA5 update even if you only are SP.
And why you ask? Well it's a blackbox but we do know it does a version check but the other reasons for its update are only perfectly clear to the gentleman, Alexnder Blade, who created and updates SH5. Rockstar not only adds dlcpacks and patches but may also make changes to the engine and to internal scripts called native functions.
So without knowing all the dirty details, Mr. Blade must identify the changes to the game and update ScriptHookV.dll to ensure compatibility. This takes time and from a post he recently made we don't even know if he is safe nor if he has internet access given we presume he is living in the Ukraine.
So please be patient, backup your files, and wait.