GI auto UV's problem? Weird result on very simple object [5.0.1p3]

Unity Engine
1

-So i have very simple object look like a Column of the building (a column was removed 2 top, bottom face and beveled 4 edge 1 time)
-The result is very weird after precompute GI: those large scale black lines.

-This wierd problem can be fix it by rotate the column a little bit:

-It’s seem doesn’t happen with the column un-beveled on the left.
-I got check option “Auto generate UVs” but it not help.

I had attached project to case 695605.

2

This time I’ve found that the objects got problem even more simpler. (A cube is stretched into a column)

Without Baked or GI:

With GI:

The normal is correct:

The problem could be caused by Directionality or Shadow Cascades:

The bug is reported.