Patrice,
In your WIP model's drone, please delete the mesh called gun_domes_dark. Its horizontal planes have improper UV's and consequently, improper AO mapping. Delete the existing gun_domes_dark_AO.png texture that the mesh uses.
Substitute the deleted mesh with the one that's zipped below and has its UV's fixed, and use it with the AO map that comes in the zip. The map also fixes a few ugly AO seams.
More fixed AO textures will come in due time.