Draughty roof windows

During 2022 for the first time we encountered several draughty roof windows. Usually we never see any draughts emanating from roof windows, so this was a bit of a surprise. The problems were with the opening closing bar that has a ventilator feature on it which we like. The windows can be open, left on a ventilate position or be closed.  The vent flap has a thin sponge rubber strip on the back of it and these are where problems lie. The rubber strips have started to decay and bits have gone missing leaving the flap not fully sealed and letting in draughts. 

Look at the grey foam on the closing flap , the left side is ok but on the right side from the centre to half way to the RH end a lot of it had decayed away and is causing draughts.