It's possible you have a bad data wire on one of the systems. Swap the data wire or both if two with a different wire. (1&4--2&3) whatever. Whatever you do inside obviously do outside. Might have extra resistamce that is throwing the error but will be fine for a ground wire.Or do one system at a time, being sure to change your dip switch settings until you figure out the problem unit. Good Luck!! If you need further help, reach me via phone at https://www.6ya.com/expert/thomas_092728000e6acb79
There should be a schematic on 2 of the electrical panels near the controls. Or possibly in the paper material that come with it when purchased. If those aren't available, you won't find it on the internet anywhere.