- wiring will have to deal with repeated bending (especially hard when it is far below 0)

- you need more space otherwise the panels will shade each other

- more components -> more cost

- more components -> more can break (and will break)

Swapping the robot for a spare is a very costly operation and can negate the power output by the panel whose robot malfunctioned over its entire lifetime after subtracting initial capital cost.

And that's assuming that you will be able to obtain 'the spare' 10 years after you put the whole system into service.