Can't comment on the main fault I'm afraid, except to say the arm should "click" into the rest position when the last record has been played and it's taken back on the return cycle (try it with the single spindle to see what I mean). The levers which deal with this should be accessible if the mech is carefully cycled by hand while you watch. It may just be a sticky lever with any luck...
As for the choppy arm movement, I'm afraid that this is a late period Garrard and in my experience ALL of them are a bit rough and ready when compared to the slick Duals and many Japanese decks with auto return - even the Lab 80 does this when the arm is smartly "thrown" back to its rest. Careful adjustment of the 95 arm maximum-height "stop" may help prevent the arm "bouncing" as its being "thrown" back and forth and again, a dab of grease in the groove of the main cam might possibly help a bit.
Good luck. I remember my SL95B with great fondness - it actually sounded half decent as my current AP76 does
despite the crude mechanism and lack of the absolute precision engineering which makes the Lab 80, 401 family such desirable products these days.