A few points to consider.
– The AGM can be held anytime in the 12 months after the Financial year for the Plan ends. Say the accounts end 31/5/19 they can hold the meeting 20/10/19 as long as a current set of accounts are supplied for the meeting. So you get 2 accounts ones ending 31/5/19 and a 2nd set ending at the date the Agenda was sent say 15/9/19. Its legal but not desirable. The delays are usually because there is major works to consider and the owners want tenders to be available at the meeting.
– If your 2018 AGM notes the levies set are due in 4 installments, say 1/6/18, 1/9/18, 1/12/18, 1/3/19 then they can’t issue levies for 1/6/19 because the owners corporation did not set the levies for that period. BUT I would make sure I paid levies as if they had been set to make sure that there was no comeback that I was not financial.