Finally it's working perfectly with these values :
protected static final float Z_INDEX_UNIT = 0.0001f;
protected static final float Z_INDEX_UNIT_ASSEMBLER = 0.00005f;
Marvin, is it OK for you ? Or should I try smaller values ?
I have reduced the values, because I found the correct values for near and far clip planes. So the depth-buffer is far more precise.
Please search the smallest value for Z_INDEX_UNIT_ASSEMBLER, for which the HUD still works for you and hold the Z_INDEX_UNIT at 10x of Z_INDEX_UNIT_ASSEMBLER.
Thanks.
Marvin