Transparency problem, help is welcome...

Hi all,

First time ever I use transparency. Please look at the pictures below.
The transparency is weird, and I don’t know what happens.
(I don’t know whether this is important but I am exporting the mesh (.dae or .obj), no animation, no rendering.)
Here is the scene with no transparency:

And the same scene with transparency (about 0.5) applied to the 2 legs on the right:

Some faces look darker than others…

A small video to see better how it looks when moving the mesh:

Any advice ?
Thank you for your help

This is more of a texture problem. You asked your question in the wrong section.

Sorry, I just re-posted in the Materials and Texture section.
Thank you for mentionning my mistake.