I found witness marks that the screw in the clutch centre had brushed up against the inside of the inspection cover.
If this is on your TR6, I experienced something similar on my 500 short after I first got it. With access to several covers from different years at the time, I discovered Meriden made the covers deeper several times, sometimes when they made other changes (e.g. the alternator rotor cover for strobe timing) but also on the quiet, without even changing the part number.
Another thing I discovered is the inspection plug seal - E8782/70-8782 - although an O-ring has long been supplied, it was a fibre washer when '69 bikes were new, and the original Triumph thick O-ring is often substituted by a cheap thin one.
Both the correct Triumph parts definitely gave more clearance between adjuster screw and inspection plug;
I managed to find some original fibre washers ...
7 plate norman hyde Kit.
there seems to a be a bit more clutch sticking then before.
Can you compare a later cover with the one from your bike?
I started looking at this as gear changes a got as little less smooth and I wondered if clutch was dragging while I was changing.
When bike is off and I pull the clutch in when in gear it takes a bit of pushing th ebike to break the plates free (which I don't remember), and once free, there seems to be more friction that I remember previously as I keep pushing the bike.
Also on my T100 before I realised the adjuster screw was hitting the inspection plug. Have you tried pushing the bike clutch pulled in but with the inspection plug removed from the cover?
prevously rear wheel would ony turn very slowly when running in neutral on centre stand, but now it seems to be running faster than before and takes a bit of effort to stop.
The 7-plate clutch has greater contact area between drive and driven plates?