The mechanical cams are compatible...been doing it for like 20,000 miles now.
I have used JB weld into the groove and then carefully sanded off with super fine paper.
Most of the hydraulic camshafts had poor surface hardening on the lobes (from the Mexican factory) and begin to "flake" off the tips of the lobes. VW should have been forced to recall these and replace them.
Mechanical cam is fine.