You can never be sure about any intervention without properly controlled experiments, but I believe that the solution for the mould formation for me was making sure bottles did not touch the back wall of the fridge. Water should condense on the wall, and then run down to drain out (at least in my fridge). But if bottles touch the back wall, it can get diverted along those bottles, affecting the labels and then possibly dripping onto shelves and other bottles.
I was also advised by the importers to make sure the seals around the door were working, by checking that they would hold a sheet of paper well. I think the logic there is that any build up of moisture in the fridge must come from outside - mostly through a open door, or through the filter, but excess might be getting in through a faulty seal. My seals turned out all to be working well, so it was not the cause of my problem.
BTW, I would not necessarily recommend it (as it could potentially result in TCA), but I cleaned the slightly mouldy shelves and bottles with very dilute bleach. In my case it worked well and with no bad side-effects.