You have it wrong. The wiper arm needs to make contact with the stationary plate, riding on the metal ring in the middle. This is an easy mistake to make until you've done it wrong a couple of times. Not hard to rectify. May be a PITA but you should be able to reposition the arm without disassembling. Check each mixer, they all have the same configuration.

the easiest thing when assembling is hold a leather washer and metal clutch plate against the rotor surface, then slide those three pieces onto the shaft as an assembly.

that'll prevent mashing the wiper finger between the leather clutch and the rotor. Otherwise, you have to tilt the rotor or bend the finger a bit to get the clutch pieces behind the finger.

if you've mangled the finger a bit, make sure it's riding reasonably centered on the ring on the contact plate. If it falls off the edge of the ring, it can contact rivets as the rotor spins and you get interesting side effects like units stepping or features enabling while the rotor is turning.