IN ACS800 OF 4 DRIVES IN M/F , IF ONE FOLLOWER F=CONNECTION FAIL HOW TO RUN WITH 3 DRIVES

I M USING 4 NO ACS800 DRIVES IN MASTER / FOLLOWER MODE TO DRIVE ONE EQUIPMENT. OFC CONNECTION IS IN RING TOPOLOGY. FEW DAYS BACK I FOUND A PROBLEM, WHEN ONE OF THE FOLLOWER RMIO CARD SUPPLY FAILS THE DRIVE IS RUNNING IN THE SAME SPEED EVEN THOUGH THE REFERRANCE IS WITHDRAWN. IT MEANS IN THE RING TOPOLOGY ONE OF THE FOLLOWER CONNECTION FAILS HOW TO RUN THE EQUIPMENT WITH 3 MOTOR MODE WITHOUT INTRUPTING THE ALL DRIVE. WITH 30.18 PARAMETER IT IS STOPPING ALL 4 DRIVES. DURING RUNNING IF FOLLOWER CONNECTION FAILS I NEED TO RUN THE EQUIPMENT WITH 3 DRIVES. CAN ANY ONE SUGGEST ME THE METHOD