Please correct me if I am wrong or use the wrong technical terms 
EMI
Electromagnetic interferance. It all has to do with magnetism.
Radio waves create a magnetic field and when a wire is placed in this field a current (I1) can run trough this wire.
There is always a return wire and also in this wire a current (I2) will be present, but in opposite direction.
Depending on how far apart both wires are, they lay in different strengths of the magnetic field. The one closest to the radio waves will have a higher current than the one further away. So you will end up with a remaining current I1-I2.
So one solution is placing the wires very close to each other so that I1 and I2 are almost identical.
Better is to twist the wires, so each wire lies in the opposite magnetic field for every twist.
This makes I1 and I2 exactly the same so you will have a result of 0
So one thing I had to do as @1.21Gigawatts pointed out was twisting the wires from the sensors.
This reduces a lot of interference on its own and actually was not really new to me.
But from here on this theory can also be applied to the PCB and this is interesting. Let me try to explain: