Ok, here's an odd problem:

I have a pack of perfectly working idle animations.
They works in game and I can see them in the CSE by opening any NPC animation tab and the Idle Animations window.

Now I packed the animation (and some textures) in a BSA. After replacing the loose files with the BSA, the CSE doesn't play these animations anymore: clicking on any animation won't play it in the NPC preview, while other packed idle animation (even from other mods) works fine. Even the textures I packed with the animations still works fine. Only those animation have problems.

I checked the path 3 times. Everything seems fine.
I tried to find any difference between my BSA and all other vanilla or mod ones. Apart from compression (I haven't tested all compression settings), everything seems equal, but only the animation from my BSA aren't played...
Extracting the BSA (using OBMM) in the data folder solve the problem (but my objective is eliminate these loose files!)

Trying to extract the animation with the CSE lead to an error: it can't extract them. But it can perfectly extract the textures.

Why the CSE can read my textures but not my animations while packed in the BSA? I'm missing something?