Sprite disappear nearly out of camera range

[Santalia]

2D Toolkit ver. 2.5.1
Unity 3D ver. 5.0.1f1

I have a problem in foreground object that suddenly disappear from camera when it is nearly out of camera range
it only happens in foreground object, which order in layer is in positive number

Here is the video
1. Normal / not disappear
http://www.mediafire.com/watch/e7ia9nbww007yhu/asset%20normal.mp4

2. Disappear
http://www.mediafire.com/watch/5575lb037q7z6iq/asset_disappear.mp4

In the first video (normal), see the upper left stone object. The object stays there until it is out of camera range.
But in the second video (disappear), see the black chain object. The object is disappear from camera before it is out of camera range.
Both object is in positive number of order in layer.

Is there any solution for this problem?
Any help would be appreciate it
Thank you

[unikronsoftware]

Hi, is that using a perspective camera?

[Santalia]

sorry for very late reply
yes, I use perspective camera and I've already solved the problem the other day
It's because my assets order in layer is in positive number. When I set all my sprites and character in negative number order in layer, the problem solved.