DIAGNOSIS Yes, this is a common, known behavior with many inverter generators in Eco mode. The engine slows down to save fuel when load is low, which can cause a slight delay in the voltage regulator responding to sudden small loads—like an RV's LED lights or a fridge cycling on.
FIX For situations where flickering lights are annoying (like in an RV), you have two options. Option one is to simply turn Eco mode off. The generator will run at a constant speed, eliminating the flicker but using more fuel. Option two is to create a more constant "dummy" load. Plugging in something that draws a steady 100-200 watts (like an incandescent bulb you don't mind leaving on) can keep the engine from dipping so low in Eco mode and may reduce or eliminate the flicker.
IF THAT DIDN'T WORK If the flickering is severe even with Eco mode off, or voltage seems unstable, you might have a different underlying issue with the inverter board or the voltage regulator, which would require professional diagnosis.
HEADS UP The flicker is generally harmless to your electronics due to the clean sine wave, but it can be hard on some sensitive equipment over time. If you're running medical devices or high-end audio gear, it's safer to run without Eco mode.