I know i know i know..
But nothing about low pitch stops removals..
Maybe the clue is in the " High or Low Idle "
At High Idle, the Cond. Lever position that should be selected during approach, Ng rises up to 78-80 %, when Power Lever is at idle.. so, Np become much higher and there is much chances that the prop blades goes out of bêta flat pitch range, to keep in the governed range.. Maybe that is the solution ?!