I presume when u say conductor u are referring to the blue, green and brown wires?
Yes those cables/wires are known as conductors, it does happen if the cable is placed to far within the terminal, that the insulation stops contact, or if there is not enough bare conductor to grip/make contact with the terminal that can also be an issue. The bare conductor must be making good clean contact within the terminal and be fully within it. So no plastic insulation inside and no bare conductor outside.
The best method to prove this would once you have performed a visual inspection then perform continuity testing across all conductors at the terminal screw heads, once confirmed and polarity is verified (these are dead tests, so isolate circuit), then you can energise and test for voltage across the lines.
When testing for voltage with your multimeter, put the setting for AC voltage.
connect the red test lead to the ‘V/ /mA’ jack socket and the black lead to the ‘com’ jack.
Then at the line/live terminal with red probe, to both neutral and CPC/earth with black probe, then test across the neutral (red probe) to CPC (black probe) I suggest that the red probe should always be the probe connected last, when testing for voltage.
You readings should be as so
Line-Neutral= around 240V
Line-CPC/Earth= around 240V
Neutral-CPC/Earth= 0V
This is a live test so be careful.