Rear skylight leaking

I recently purchased a Peugeot Warwick Duo but a leak appeared after the first heavy rain last week. Took it back to the workshop where we bought it from & they stripped the rear skylight, cleaned all the joints, put new tapes & mastic on. The wood surround in the opening showed no sign of water & rain was not coming in through the clear plastic lid seals. Heavy rain today & water coming in from inside the unit again. It looks like splash water is getting in via the joint between the top & bottom halves of the unit. I was prepared for this so had a sheet & bucket ready so no damage done to the seats & carpets. Does anyone know the manufacturer of this unit (it's the large rear skylight with the winding handle). Has anyone else had problems with rain water coming in via this route? The workshop did a good job of sealing but I believe this is an inherent problem with this model of skylight.