Wierd light bug. Light shining through mesh.

Hello everyone,

I have that strange bug, that when I place a light inside the object prepared for the lights, the outside of the mesh starts to shine. But as far as I checked, there are no mesh errors, or open parts where the light could shine through. I am helpless I have no clue what it could be.

First I just placed a point light inside this tube but when I baked the light, I was shining outside. So I used a spotlight and put it outside. But that did not work well, because like this, the room is illuminated but the lights look like there were out. This is really strange looking. So I tried to combine both. Illuminate the room with spotlights and use a point light with small attenuation radius to illuminate the lamp itself, but that did not work because it started to glow again on the outsideā€¦

I would be so glad if anyone knew why this happens.

Btw: I am a total Unreal beginner, so I am pretty sure this could be a totaly obvious crap :x

Thank you in advance.g