It’s usual for a single Invoice to be received showing separate line items for each of the Administration and Sinking Funds, and a total amount payable as the combined Levy.
Have you or any of the other Owners checked the Schedule of Unit Entitlements that would have been included as an Addendum to the Agenda of your last AGM?
That would clearly show the applicable components of each Owner’s combined Levy payments and reveal any accounting errors by your newly appointed Strata Manager, which surely they’d have corrected by now if any Owner/s had queried their original Invoice/s and those were in error (?).
It’s by no means unusual or even unreasonable for some Owners to adopt what you describe as the “monkey syndrome” and expect their Executive Committee (E/C) to either attend to the day-to-day running of the Plan or to delegate that to its Strata Manager, and if a Member of that E/C doesn’t or won’t work well with the others then they won’t be re-elected; will they?