Its quite common on the PT to have the rear seal around the wiper fail resulting in either water entering the boot or a wiper motor failure. The cure, of course to replace the seal or….you could do this........
Pick up some chrome radiator pipe collars from B&Q
Cut away the inner “wings”, cut off the clip and check that the hole is big enough to fit over the wiper drive shaft (some PTs will need the hole to be a little bigger) After the dry run, put a ring of sealent around the underside of the collar
After removing the wiper arm, repair the seal with some silicon sealant
Now stick the collar over the drive shaft with the joint to the right (it will be cover by the wiper)