Don't know this specific wiper, but have had several Fiat
wiper assys apart. Most have a snap-ring/circlip retainer,
stainless washer, nitrile O-ring, on the outer end of the wiper
shaft, inboard of the splines that hold the wiper arm.
If with age water gets past the O-ring, big problem, it's
an iron shaft in a diecast tube, a poor electrochemical
combination, it corrodes and greadually freezes solid.
If you get the whole assy off be prepared for a bit of
dismantling, and note which thin stainless thrust
washers go where. It's not too difficult a job, bet it takes
a fair bit of time.
Fiat self parking slip ring/finger assys may need
careful adjustment of the phosphor bronze fingers if
it doesn't wipe, or park, when it should.
For the iron wiper shaft I re-lubricate with Castrol
Heavy (LM seemed a bit on the thin side) with some
Silicone MS4 for its water repellent properties just
around the O-ring washer bit. You may also need
an assorted O-ring kit, if the O-ring is aged or worn.
Most problems have been with the front wipers,
that get driving rain, at 70mph or so, trying
to force water past the seal, so after about 5-10
yrs they start to develop this problem.