Short after this i just went and did this small change:
From this: modelShader.loadUniform4f(animationStack[index][i], modelShader.getUniformId("gBones", i));
To that: modelShader.loadUniform4fTransposed(animationStack[index][i], modelShader.getUniformId("gBones", i));

Turns out that for some reason Assimp4x4Matrix (which i was using) are reversed major , i have no idea why this would work in my old engine as normal (non-trasposed matrix) I am actually confused here ! The animation works fine now ....

Here is the man , who has only 1 vote and saved my day, thank you!