Certainly the stretch of line north from Rickmansworth is still subject to such problems to this day and on the LT sections, at least, additional controls are introduced into the signalling during the leaf fall season to guard against the consequences of such a disappearance.
Yes! It certainly does...and only a few weeks left before it all starts again! The stretch between Chalfont & Chorleywood gave us (and yourself as well!) interminable trouble last year. With regards sequential we have to put 3 cars on all trains until a cut off point in the morning, to ensure the T/Cs are occupied, but I understand that even still causes grief sometimes.