We had exactly the same problem with the Uniport.
Had to go down to Droitwich and take the board out and send it back with a Dell computer that it wouldn't run with.
Roy had to modify the board and rob one of the inputs to amplify the signal.

Then had the same problem on the System 1 board and 3 or 4 had to go back and have the same thing done.
Managed to get Roy down and sort this at our place so that saved a trip.

Then had a problem with the spindle speed board not putting out 10 volts when the cable was about 6 feet long. This time Roy wouldn't come down even though the machine was due to go right up north.
had an electronics guy look at it and the 12v to 12v DC convertor was the smallest available. Changed this to a larger unit [ cheaper as well !! ] and that cured the fault.

So my experiances haven't been that good. I now have my boards made for me, not cheap but 110% reliable.