The main problem is that SH5 in general is totally ****ed up. In my opinion UBIsoft just harvested money by packaging old code from previous SH versions , added some multimedia content to look its actual and left the game partially unfinished.
And now you mod-guys do their work to put it together and teach people how to workaround their bugs..
Unfortunately this will be never-ending story, new fans will always come here asking their questions, its absolutely understandable they are not prepared to read long manual to how to save their game, because UBI's product just merges saves data in case of overwrite. (etc..)
Someone just need to love this game to overcome this as i do..
I have to thank you for all your effort.
