Successfully enabled mirror dip on MY18, but it will only go 10mm lower and that's it.

 

Works on my other Golf MK7 and Audi A3, why doesn't it go further on the Octavia MK3? Anyone ever figure this out?

Nope...   Same on our kodiaq...   I think you need to have electric memory seats for it to go further and the dipped position set.

Yes, you need a memory seat to get the mirrors to go back any further.