After the latest WD15 dock update there are two bugs:
1. The Dell Dock Update 'Updates Complete' popup continually appears when any device is connected to the dock or the attached XPS 15.
2. All audio is lost whenever any USB device is plugged into either the XPS 15 or the dock itself. Audio continues to play (ie through spotify) but there is no sound. Unplugging the audio jack on the WD15 and reinserting appears to fix this bug.
After the last update to the WD15 have similar problems. The annoying popup keeps popping up. he audio driver of the XPS15 (used when the dock is disconnected) is now broken (produces an error).
Looking at this and other threads, it seems that nobody from Dell is watching this. If they are: Please fix this!