...You are Not going to like hearing this, and this has nothing to do with a slipping clutch...
FWIW, In the Photo, the Half-Shaft Flange Mounting BOLTS are Installed from the Wrong Direction. YES! It makes a Difference. The physics of Bolt Fasteners dictates..."The Bolt HEAD Must contact with 'The Most Rigid Base' "*. That Base would be the Transaxle Drive Flange. The Bolts are to be Installed from 'Behind' the Drive Flange. Since you will be pulling everything apart, it will be an opportunity to correct this. Not just My Opinion, just Good Engineering.
* And in the case of a 'Rotating Assembly', such as a Helicopter 'Rotor-Head', the Bolt Head Always Points in the Direction of Rotation. If, in the Worst-Case Scenario, the Nut should vibrate Off, the Bolt would Stay in position.
The Praise: It looks as if You have Eliminated the 'Split-Washers'! This is Good!! I, also did this, First Thing! The 'Split Washer' is a Hardened 'Spring'. I Have seen more than One, Break, Fall Out, and the Bolt Immediately becomes LOOSE, you don't need to Guess, what Happens Next!
This is a 'Heads-Up', for All those who care to listen.
MJ