I think it’s normal. My
Cupra does this when it’s raining and the auto wipers are engaged(with rear set to off). I do think it only happens in two occasions and to me that is:
1. I am going above a set speed (I think above 50/60mph but not sure)
Or
2. The level of rain. If it is raining a lot it intermittently wipes.
This is what I have decided why mine does it. It is only a wipe every now and again, probably twice a minute or so. As I said I’m quite sure it’s normal at least on my 2016.
And obviously If wipers are on the rear auto comes on in reverse gear.