if 1m is coming in, make sure the brake is picking, if the brake does not pick the error voltage will exceed 40 millivolts and trip the comparator. thats where i would start. if the brake is picking, then it could be many things, like john has noted. good luck i have a couple manuals if you need i could send them to you the brake not picking is usually the issue i have found when it is intermittent.