layering of 2D sprites in 3D

I’ve bumped into this countless times and never was able to find a solution (or fully understand the problem)
Any ideas?

There’s a frites sprite, that lives a little bit in front of a white tent.
At some angle/distance combo, the frites will disappear. Why does this happen? How do I make it not happen?

Both gameobjects are regular sprites with the default sprite shader/material.
I made them non-transparent in the 2nd gif to show it more clearly.

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May be a clipping bug. There is a post about a similar instance in the link below.

Their solution is to press ‘F’ to focus on the object when selected, this seems to solve the clipping problem.

http://forum.unity3d.com/threads/sprites-disappearing-when-zooming-in-clipping-problem.234593/