I don't know how many pixels the chart node would be using for the 24 hr line chart. No problem to reduce the sample rate for sure.
NR and Dashboard are the latest versions and the browser is running on my laptop, not on the Rpi3.
I think I may have found the culprit as well. I have an AC voltage sensor board (is commercial hydro okay?) feeding an Arduino NANO board that uses USB to send the resultant data to the Rpi. It was providing around 12 samples a second all the time through the USB port (desired to measure glitch durations). I rewrote the code on the NANO (and my NR function) to only update on a change of AC status. Detection by the NANO and reaction of the NR function is fast enough to still keep the measurement reasonably accurate. If the "glitch" lasts more than 10 seconds it becomes an outage which then causes various things to happen. I'm not entirely sure this was it, I'll have to see after a reasonable period of time if the problem re-occurs.
