High res won't "clean" the signal as much as average does and that's why average is nice to "make the signal thinner" by removing the less constant acquired points and keep the most stable ones. It's a way of loosing fat
Yes, that's where we reach the limits of my $150 scope.
You need a stable trigger for average mode.
But it doesn't manage to do that in the uV noise salad.
But I remembered that it has a line trigger mode (50Hz)
This works a little, but you can clearly see the limits.
In the attached screenshot: 1.02mV/div ("zoomed")
If you squint your eyes a little, you can see the capacitors discharging.
But for $150 it's not that bad...