It's the defrost cycle and it's normal.
The defrost cycle will happen approximately one a day. (older refrigerators were twice a day- every 12 hours)

Other than that you have your freezer set too cold !
It looks to be running between -2 to -7 and it really should be set to be +2 to -2 averaging 0F. Setting the freezer where you have it is using too much electricity and that temp provides no advantage over the 0F average.

Thanks!
Where I live, the relative humidity (outdoors and indoors) is pretty low.

Couldn't I get by with defrosting less often?

But, I guess there's no way to change that.

Cheers,
David

The defrost is either a straight timed cycle or in some refrigerators an adaptive cycle that is based on your usage of the refrigerator/freezer. There is no adjustment.

A lot of engineering goes into how often an evaporator needs to defrost so you don't want to change anything.

Try the penny test to see the overall effect.
Freeze a cup of water and place in the freezer with a penny on top. See if the penny sinks into the ice- that will show just how much the defrost cycle is effecting your other food. (From the appliance doctor)
The defrost cycle is normal but maybe the temp is off or it might just be a short moment from the air movement during defrost mode

I Love It!
What a nifty test!

On my way to do it now.
David

Don't laugh too hard. I retired from a major medical center and told a compliance person about this test and said that checking temps manually was unreliable. Next thing I see was that all freezers needed to use this test..
Now they use a temp tracker but I did have a good chuckle.

Let us know what you see!