Somewhat drastic, but try
-forward merge merging in a blank AC13 template file
-if that doesn't work, save out a pln and then reshare. Test in the pla that you can fix the linking problem first before resharing.
Perhaps someone else here has another suggestion.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"