Hi, @reedjc
Look at this image.
Move wire A over to be next to wire B, that is to keep the load wire AWAY from the controller.
Tidy up wires C so that they do not intermingle with the load and power wires.
I would change the layout.
Turn the relay module around and have the load and its power wires come in on the left side, so that the load current goes NOWHERE near the controller.
The signal wires to the relay module will be then at the other end, AWAY from the load wiring.
That looks like a metal case, have you got it grounded, at least to the DC supply negative?
Tom.. 
PS. Can you see why the system resets? Load power wires with 0.4A next to control wires with approx 1/100 of the 0.4A current running through them.