In the 15 V3 boards the front panel LEDs were protruding a bit; this was bringing a slight misalignment on the screw holes of the front panel and was making the screwing of the front panel slightly difficult.
As Betty Magnin pointed out this is due to the tolerance of the body of the LEDs and moreover to the position of the LEDs in the PCB.
Note that the position of the LEDs is exactly the same as in V1; in V1 we had not noticed any issues as by chance the assembler was systematically pushing the LEDs to the rear when mounting them.
Betty Magnin suggested a modification of the PCB design to move the LEDs more inside the board.