Brother-in-law's Passat had repeated issues with bad seals on the caliper motors, so they rusted inside. Eventually the eBay versions worked well & seals have lasted better than OEM !!Vag group motors have has them for well over a decade
Wife is on her fourth with laccy calipers, all been good, but do need diag tool to wind pistons in to replace pads, you can billy bodge your way around it if you are desperate enough