After verifying that there are no local modification to the source files of h1iscex and h1iscey, I did a clean "make" and "make install" on these models and restarted them. This fixed the broken IPC MEDM screen (where it appeared the ISC model was trying to receive its own sending channels) and fixed the 100% IPC errors at the ASC receiver for the LOCKIN_OSCn_CLK channels.

Looking at the time stamps of the files, we suspect the problem appeared due not leaving enough time between the make and make-install steps (possible NFS caching).