BOSS8 Bridgeport quit in the middle of a part. I can enable drives, but drives drop out when I hit EXEC button. I get "+Z OVERFLOW" and "E STOP" error message when I enter the FIST monitor. Right after enabling the drives (but without hitting EXEC) I can JOG X and JOG Y, but not Z. Replaced FMDC, EAF and EMC cards, no help. Any ideas?