Camera custom matrix, shadows not working anymore - Unity5

Hello, First time I have to ask people to help me with a problem, I usually try to find by myself but here I think it could take a lot of time.

Some months ago I made a custom matrix projection for my camera (Camera.projectionMatrix) and it always worked perfectly, no shadows filckering, no objects disappearing so near and far clip planes work finely. I just had to increase the values for the far plane and in Quality settings increase the value for max distance shadow to avoid having them flickering. I can't avoid to use my custom camera it's the "key" to play my game, the matrix is ajusted to give a specific view of the scene according to the position and orientation between the mobile screen and the user face.

The problem appeared with Unity 5, now I don't have shadows anymore whatever the values applied to far plane and max distance for shadows, when I switch back to the normal mode by deactivating my matrix modification in real time I can see the shadows but with my custom matrix I have no shadows. My objects are ~100 unity far from my camera, my near plan is 0.3 and far plane 1500 I found my shadows reappear when increasing the NEAR plane to ~20 but their behaviour is really strange, they rotate according to the camera orientation.

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Do you know if there have been changes with the way shadows are computed between Unity 4 and 5? If so what had been changed or is there a way to go back to the way they acted in Unity4. If I find nothing I will have to go back to Unity 4 but Unity5 seems more interesting and next updates won't happen on 4 so it would really be better to find a way to make it work with u5.

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I don't think it would be useful to let my code on this work with matrix projection since it's not simple at all to understand why I put this or that value here or there but I can at least give for an example my custom matrix and the original one but I don't think it will help.

 29 fov, 27 near, 1500 far.

Here is my matrix with a normal behaviour :

 2.17622    0.00000    0.00000    0.00000
 0.00000    3.86671    0.00000    0.00000
 0.00000    0.00000    -1.03666    -54.98982
 0.00000    0.00000    -1.00000    0.00000

and here is the custom one with the same situation :

 2.13346    0.00000    0.00000    0.00000
 0.00000    3.79075    -0.00144    0.00000
 0.00000    0.00000    -0.51833    -27.49491
 0.00000    -0.00038    -1.00000    0.00000

As you can see no big differences but it seems like the way shadows are computed with the matrix projection changed between Unity 4 and 5.