EM64 need to be reset after hot swapping. An EM64 knows which column it is in by a connection on the backplane. The problem that happens when hot swapping is that the Power connector receives power before the Data connector confirms location, and the EM64 will boot up assuming that it is in the first column. (The first column has no wire loop connection required on the backplane)
HERE IS THE INFO ABOUT L86 RACKS AND HOW EM64'S KNOW WHERE THEY ARE.
3 EM64s are addressed the same, but jumper on 96 PIN connector in rack tells it which dimmer row it controls.
Column #1 EM64 has no wire jumper.
Column #2 is wired from 32B to common (30A or 31A).
Column #3 is wired from 32C to common (30A or 31A).