PV voltage fluctuation

I have a SmartSolar MPPT 100/30 & 100/50 with two 410 mono panels connected in series.
From the controller software I can see PV voltage constant fluctuation.
Do I have bad connections in my cabling or is this function of the controller?
I tried to look around manual and Victron support, but I did not find any answer.

It depends, is it fluctuating all the time or when it is retracking the pv? How big are the fluctuations you are referring to?
Once it has a stable power point it usually stays there unless cloud cover or other changes happen. (Then about every 10 minutes it retracks)

And more of that, was the MPPT in full working mode or was in current limited mode?
It’s important because there are two different algorithms used for tracking.
So when did you saw this behavior?
Give us a little more about your system beyond panels and mppts.

Fluctuation is about from 30 to 70V. Panel nominal Vout is 35V.
I did see this just after taking MPPT out of the box installation.

I did go to the site today. We have had a clear day and PV voltage was nominal.
I did look at the Victron app history. Looks like in very cloudy day the LUX value is so low that MPPT is going into the float mode. PV output is just too low.