You may wish to seek some particular legal advice on this, but, the act does not prevent the OC to resolve to transfer funds from one fund to the other, and having consideration of current fund balances and the forecast expenses for both funds, not to strike a special levy to reimburse the fund.
the above suggested, I would actually recommend that you transfer the funds by the mechanics of adjusting the apportionment of admin versus sinking fund levies, ie, reduce the sinking fund levies and increase the admin fund levies by what ever proportion you wish to transfer.
it sounds like your strata manager has taken a very by the book approach on this situation, in that they are following the act specifically by the book… However, I bet that they haven’t actually followed the act so precisely, in that they have probably expensed repairs and maintenance from the Admin fund rather than the Sinking fund, being the likely cause of the deficit, (see section 65 of the Strata Schemes Management Act). In the first instance it may not hurt to review past periods expenses to ensure that they have been paid from the correct fund.