Mine drops a bit now & again & it’s less than 3yrs old
If you squeeze the rubber channel bit together where it pushes on along its length every couple of inches to bend the metal ‘gripper’ (its inside the rubber BTW) & tighten it a bit it should stay on.
If that doesn’t work then maybe the internal metal gripper has given up & the whole strip will need replacing, short of glueing it onto the fibreglass, but if that’s the case the rubber itself has probably lost all flexibility & would be better replaced anyway.