Thanks to everyone that have helped me with this issue, you guys have been really helpful. I´d like to specially thank the Epic Evangelists team, their word made me see the light and all issues were fixed, such a great great professionals.
To anyone out there that has this issue in the future and don´t want to wait for anyone to show up and give you some ideas, I´ll give you some as you will feel as alone as I did:
- Don´t do any of the stupid steps I´ve specified I did, nothing is going to work no matter what you do.
- Migrate the level where you have everything (or levels) to another project
- In my case I´ve had the rooms of the houses separated into levels, so start building light from separated levels, saving constantly.
- By doing so I´ve realised when I was trying to build light after imported the whole kitchen, thoses errors appeared on the swarm agent
- It turned out one blueprint that contained my electric appliances was duplicated, same place so visually impossible to distinguish with all assets in between.
- Same with bathroom and bedroom levels, one static mesh of blueprint containing static meshes was duplicated.
- The duplicate wasn´t my doing, it was Unreal´s bug while building light for 3 days straight and crashing at 99%. I tried to push my CPU too much and I paid the consequences.
One lesson I´ve learned is that you really need to do back ups, get an external drive, cloud, whatever but do back ups of your work. Don´t get me wrong I had two backups of my work but those were 10 days old and the ammount of work I put between those 10 days was quite considerably to just toss it out and use the old one, but I should have done a backup of what Initially I was happy with, I just wanted to push forward the engine and get better results, never again.
What I also noticed is Unreal still has a lot of work to do to integrate better with Datasmith. Since it´s release I have been using the Datasmith plugin on a daily basis, but if for any reason you move or change name or simply migrate your project to another one, Unreal might have issues with some Static Meshes, not all but with some, for some random explanation that I can´t understand.