I just upgraded from El Capitan to Sierra 10.12.2. Until now I could use finder to open Time Machine sparsebundles on a Time Capsule. Now I get "The application "DiskImageMounter.app" can't be opened." -35. I can still open sparsebundles on directly connected disks.
I have done several tests compaparing 10.12.2 and 10.11.6 on two diffwerent machines using virgin installs.
I am wondering if maybe something changed in Sierra, and if it was intentional.