Rear wiper + parking sensors

Hello

I've spent most of the day going through posts on this forum regarding rear wiper issues.

The car is a 2007 Octavia Estate. I first noticed the problem a while back, but ignored it because I'm an idiot.

The behaviour is as follows:

Car starts, sometimes the rear wiper might try and move back to start position.

During dirving sometimes the wiper will activate and move, sluggishly and sometimes make it back to start position, or not, then stops responding.

The rear water jet comes out from above the rear windscreen, a small nozzle sticking out to the side of the eye level breaking light.

Other info.

The rear parking sensors gave up the ghost a long time ago.

I may have found water ingress towards the CD changer.

Things I've done so far.

I've removed the rear wiper motor assembly and taken it apart - to be honest it appears to be the improved version, with plastic backing, the seal looked good and it was like brand new inside. Clean white grease, not a single speckly of rust or dirt or water inside. Right now I'm saying that THIS is not where the issue is.

What I plan to do next.

Pull the lining out and get to the water feed pipe and inspect for any breaks/leaks.

Then what? If it turns out that this pipe is OK, then I might have other issues, what I need is some pointers to what else I could do to diagnose

thanks