@NavisCraft that cause these building are valid only if you open the prop menu in a specific place ( open the prop menu (f) where the original build spawn, same for raod, land or whatever)
So by "validating" you removed them all cause map editor dont " check " them at good place and think they're invalid, you've to find each area location ;S
BUT
I'm doing a mod that is aimed to bypass this validate system (prop always valid) and that put the colision on these object ( 50 K object is nice but without colision it's hard to use xd)
so with time we will be able to do whole new town
https://www.gta5-mods.com/maps/custom-prop
this is only the v1, v2 is coming soon