Transparent material causes 'slashed line' in the middle, how to avoid it?

[filibis]

I wanted to make a frosted glass but it’s way harder than i imagined, so i decided to just put a ‘blurry’ texture with transparency (and play with alpha value inside Unity).
However transparent material causes a weird cross line. Why this happens and how can i avoid it?

[filibis]

I think the problem was i mistakenly applied material to both faces (front & back) in SketchUp. When i delete/purge all material applied to it and reapply only to front faces in SketchUp, the problem is gone in Unity.