I found what give the problem… There’s nothing moving the light, but I found a blueprint in the level that change some static meshes randomly in the costruction script… This explain why each time I open the level it asks light building… I apologize for turning such a trivial problem into an odyssey, but this is a project that more people are working to and I didn’t notice this blueprint. Thank you a lot for help!
No worries 
Of course if you want to move them with BP they need to set to moveable, which means the light wont need rebuilding…
Happy days!
Yes, of course, I did it! Thank you again for help!
Have a nice day!