I believe that someone gave you some good advise by telling you to check the power supply. The low volt power supply distributes both +12 and -12 volts. Both of these need to be checked. 11.95 volts might actually be far enough out of range to cause a problem. The voltage might also be fluctuating throughout the day. If this machine has the old computer style low volt power supply (it is shaped like a box), it can be updated with a kit that Haas has available which has the new style power supply, cables, and an adapter plate.
I have heard of coolant float sensors shorting out and causing this problem. If your machine has a coolant float sensor, you can run the machine without it for a while and see if that helps.
It is best to leave the replacement of any boards in the cabinet, such as the main processor or the mocon to your Haas dealer. They provide a warranty for all parts they install. They cannot warranty parts that are installed by the user.
I hope this helps get you closer to solving the problem.