Hi, Stirling
I posted this in the wrong post yesterday, You may have already seen it.
Not knowing how your Magnetic sensors are wired, Thy may still be floating a low or high signal that close, Try adding a 2000 ohm resistor to there output to
Gnd. or +5 volts holding them hi or lo, Until a stronger signal pull them full on or off.
Using some Prox switches hear, There Opto Isolated and have a Pull down resistor on the switch side.
Hope this Helps, Chip