It has been my experience that in normal flight conditions for police ops, cruise-hover-orbit-cruise, that the fwd xfer pump will give indications of run dry at around 125kg fuel in the main tank when in the hover, orbit cycle.
Of note is that the 135 on level ground sits at around 7 degrees nose up and of course many things will effect its attitude once off the ground, including CofG and relative wind.
It's also the case that the fuel qty sensors don't often just go wrong overnight, they degrade due to contamination over years (perhaps why the manufacturer specifies 6% inaccuracy as to be expected). In my experience they seem to be less accurate when asked to display abnormal situations (in police use) such as when attempting to fill the main tank to full, or with abnormally low fuel in the supply tanks. A change of sensors by the engineers has always brought things back to normal for a couple of years.
Some on here are still jumping in with 'startling revelations' that have been covered only a few pages ago, and a few pages before that, and....please read what's been said before wasting your efforts.
And to suggest that the less than half dozen 135 police pilots on here don't understand the fuel system is blatant baiting of those who are trying to explain (often in simplistic but factual terms) to an audience with no knowledge but a huge interest. About level with those who drop in every few days, blame the pilot without reservation and clear off again until appearing a few days later without reading anything in between and make the same blunt pronouncement.
Like Sid, I'll be back when something factual emerges to add to the debate.