Hi,
Me and my wife share 1 photos library that sits on an external hard drive.
Problem is that as soon as one of our users assigns this shared library as system library the other user can't access it anymore.
It has nothing to do with read/write rights on the external hard drive.
The file is for both users accessible.
If not assigned as "system library" the sharing works just fine.
Thanks for reading.
iMac with Retina 5K display, OS X Yosemite (10.10.5)