Weird shadows on wall corner ?

After building light with Production quality, wall corner shadows have something wrong.
Could you tell me how to fix this problem, please?

I attached sreenshot with my lightmass setting.

Hi!

Are your walls corner snapped to each other or overlapping?
What is the lightmap resolution per wall piece?
…are you using portals? Is lightmap compression turned off? /I’d turn off ao also while you’re just testing your lighting…

I have checked it, no snapped, already using portal. The lightmap resolution is 256, yellow color in Lightmap Density. then I will try higher resolution. thanks your reply.

I’d say it will be the lightmap resolution then!
Also I would suggest to have your walls corner/edge snapped and not overlapping!! You’ll lose uv space for the “invisible” parts + you’ll have a bigger chance to get artifacts on the edges!!
…while you’re just testing the lighting you can save a lot of time if you’ll go with quality 1<4!

I was increase Indirect Intensity then it was not improved completely but very much.
Thank your help.