Sorry for not replying sooner ,
Yet again i have to give you a huge thank you :).
writing all that out must of took a long time and although i can’t say i understand it all yet, i will be trying hard to do that soon, Your huge and kind effort will not go to waste (although don’t be shocked if i ask for help 
And i truly say if there is anything i can do for you in return, please ask (like if there is anything you were wanting from the project now, i’ll happily put up a link or jpgs showing the code ect)
The thing i have been trying to do last night and today (and need to do first before attempting your words) is trying to solve a big problem in the Retread project. i did notice it before, but i did not know how bad it was. basically most of my presets don’t work normally or good after respawning, and even worse is that they don’t work normally when dragged in from content browser ?.
It does seem i have ended up with 2 versions of the same BP ?, The one that is already in the level works fine, But after respawn or a new copy dragged in, they don’t work properly any more ??.
I think i might of edited some of them via the level editor, rather than opening the BP it self (double clicked on BP while it is in level then changed some materials ect in the details panel), and that i do know will change material on the BP in level, but not change the material inside BP. and that’s the only reason why i can think i seem to have 2 versions of the same BP, But that still doesn’t explain while they are not even very driveable after Respawning/New versions from content b are dragged in
I have read that BPs can get damaged and also know about the back ups folder (but i am sure i won’t have old enough backups, let alone they would be missing a lot of what i have added since)
Plus the Advanced BPs are over a year old, but the same problem is happening to the Sedan version (made with 4.22 template BP)
and also it is not to all the advanced or sedan BPs ?
So anyway i just thought i would ask if you or anyone that might read this if you have come across this and have any possible answers.
I don’t want to delete the BPs (They are the ones i have worked most on).
Worst comes to worst i will just try and make 3 good BPs (1 of each Vehicle base type) that work in any level (plus i will leave everything else in project for people to make up the other preset versions themselves if they want to),
But what happens if it happens to them again. Basically it would be best to solve this problem first rather than remaking and hoping it doesn’t happen again lol.
Here’s a video if you or anyone are up for helping with this mystery
and Thanks again