The make of roof you have is 'global' now owned by synseal, two ways of dressing the lead over the wall starter rafter, either right over covering the white capping as you'd expect or as you have it right now, the roof system incorporates a secret gutter built into the aluminium section so although the lead looks like it's just tucked behind the rafter and will leak like a sieve it's actually laying in the inbuilt gutter. I've attached a tech drawing of the make up of said rafter and gutter for your information. You'll need to remove the end cap just above the plastic gutter(a screw behind an oval cap), then peel the long rafter cap up, you'll then expose the gutter and possibly see why water is not running all the way down, could be a frame fixing in the way, a blob of silicone on even where the lead is overlapped and is twice the thickness could be causing an obstruction?