And remember with a slipper the first plate in is different to a std clutch.....has he just fitted it as it was as per the std set up ... and the first plate dropped down behind the centre hub?
Which one I’ve seen slipper clutches with up to four in them .. and the clutch still slips with high engagement because of incorrect build. I saw a1098 with two in at portimao once .. they put the wrong plate in first and it dropped down behind the hub ...