The trouble arises with ring-bound organisers in A5 and A6 when the block of inserts is too thick, or when the sheets are not sitting centrally as it closes: the bottom pages no longer slide back, the cover pushes them outwards, the punched holes tear through and plastic dividers get bent.
Three things help. First, do not overfill the block; from the diary insert only the months actually needed and keep the rest separately. Second, hold the organiser upright for a moment as you close it, so that the sheets hang down and settle towards the middle of their own accord, and only then fold it shut. Third, plastic dividers slightly wider than the inserts are a great help: they enclose the block like a wrapper and protect the punched holes in the paper. Before closing, pull the rear, wider sheet back outwards and fold the block over onto the front sheet; nothing then needs straightening from the outside. Dividers of this sort also have reinforced holes with a little play and do not wear out themselves.
Holes that have already torn can be secured with self-adhesive reinforcement rings; badly damaged inserts are best replaced. Suitable inserts are available in the same format from other suppliers as well as from Montblanc itself.