Massey 2846 low voltage issue

My buddy has a 2846a massey baler. Its hooked to a JD 7400. He will ocasionally get a low voltage alarm on his monitor. Normally while it was trying to tye a bale with net. Recently it has gotten worse I had him run a #10 wire from his battery straight to his harness plug constant 12 volts. He said it worked perfect for 30 bales and now he gets the alarm while baling as well. At any point while watching the monitor voktage is always 13.6 +/- brand new batteries. All conections have been checked. My next move is to have him run another wire for ground and another one temporarily for switched side straight to battery to see if that gets it so we can eliminate the factory wiring. Ive been told the 12 volt constant side was too small from the factory anyway. Maxzillion if you read this does the ecm monitor the voltage on constant hot side or switched pwr side of the harness. If that doesnt get it im pulling his alternator off and having it tested at a local rebuild shop. They should be able to load test it. Whats funny is he has never seen his voktage dip at any point which makes me wonder if factory harness ground wire is too anemic. Can anyone think of something i am missing. I have issues with my 1086 as well with my baler a new alternator resolved the issue for a while.

Massey 2846 low voltage issue