I noticed my inverter would make a similar ticking sound when running my bean to cup machine. What is interesting is that it will only make that sound when the display on the inverter is on, ie I press the enter button to bring up the screen display to check load or battery power level, when there is no screen display selected the system doesn't make any sound when running the bean to cup machine. No idea why this is but thought to mention it as perhaps the type of power those appliances draw causes interference when the system powers the screen display.