The two ground wires need to be separated otherwise you will induce a lot of noise into the system possibly causing erratic operation. The white and black should be completely separate all the way until a the grounding lug, at that point you can put them in the same lug. If you are tripping the failsafe the yellow light will come on for 4 seconds then go off unless it re-trips right away. Make sure your WL and WH are set properly.

Again, if you unplug the level probe it will eliminate that from the possible issues.

Make sure your ground terminal for the black and white wires is at 0 OHMS to the chassis or battery negative. Any floating issues will be picked up as noise.