Shrappers

Hi all, I have 2016 Octavia hatch back. The rear wiper has started to switch on by itself. This happens even if the wiper stalk is set to off for front and rear wipers. It seems completely random. Sometimes it will turn on for a bit, then switch off after some driving. Other times it will keep running on and off. I read that sometimes the rear motor could short out if the washer fluid leaked. I've changed the rear wiper motor now as it was an easy change but I still have the same problem. I'm thinking the steering wheel controls might be the next step but this is a lot more expensive and time consuming. Has anyone heard of this before or have any suggestions for things to check? Thanks, Paul