The reports you have, most specifically from the engineers, do not state that any repairs are required to the balustrades.
[note that an expert will never say something is “safe” because that would leave them open to liability]
From what you have said, it seems that some people want to upgrade the balustrades. That is not a repair. Bringing up to current standards when there is nothing inherently wrong with the balustrades is not a repair, it is an upgrade. Look at it another way – what is being repaired?
If the owners want to upgrade the balustrades then that will require a special resolution.
The strata manager should also be told that they should not be giving advice in relation to liability unless they have a sound basis for doing so.