light map not showing

a problem suddenly poped up while i was working on a test project (i’m still very new to UE) i had a lighting setup and all the light maps where working fine,
until the launcher updated and started seeing this black thick line at certain angles on the wall (unfortunately i didn’t take an image of it), i though that it’s probably because of the update and so i restarted UE4 and it told me that the project was made with a different version and i choose “copy”, and then I build my lights at production quality, and then i noticed that one wall had a missing shadow:

the light is there (almost correctly) in the “lighting only” view

but is missing in the “detail lighting” view

i rebuild the lights in preview quality and the problem presets

thanks in advance