Did you check the ripple on the PS1 power supply? Replace it if there is more than .010 vac. If all your confidence tests are a GO and you’ve already cleaned your card connections, try unplugging the load weigher J4.
Make sure your wiring looks like this:
https://www.dropbox.com/s/10jcfhw7ofvvyd0/Group%20Comm%20Wiring.pdf?dl=0