It's true ..... the magnetic pulses from underground objects cause your finger to wrongly input the correct three digits on the flight director.
My solution has always been to wrap yourself in tin foil when looking at the SID pages in your Jepperson manual.
The problem exists mainly when flying a compton 1 romeo, but a woburn 2 fox seems to be unaffected.
I am off now to polish my five bar epaulettes
titter