If at all possible, I suggest trying to find a sympathetic ear on the committee. If one person will listen, then that person as a committee member has a responsibility to supervise the treasurer and other office holders and see that money is spent with proper authority in accordance with the budget approved by the AGM and so on. They should have access to the accounts, most likely through the manager’s web site with a committee log on.
Another option is to do that yourself having been elected at the next AGM.
Another option is to visit the managing agent’s office having arranged to inspect the OC records. Any owner is entitled to do that. Take notes and then ask specific questions of the treasurer about what particular payments were for if they are not annotated sufficiently to work out.
The strata manager might be slack but they might also be in a difficult position. They act for the OC as instructed by the committee and have to do as they are told, unless it would be clearly illegal.
If you do some poking about, that might be enough to have the committee and manager being a little more careful to have things tightened up and more clearly kosher.