I think the maintenance bill asks for separate checks for each week you own and that may be the problem,as they do not like to co-mingle funds
I had a similar problem on late fees but had fortunately registered the envelope
The payment was with a US Funds Bank Draft purchased in Canada and was able to provide proof they received it on time so the late fee was reversed.
In previous years I always paid by credit card,and had no issues,so next year I will be using credit card again as it just seems to run more smoothly

I am sorry to hear of these issues, and that the proposed solution is to pay by credit card, because it costs the association money when owners pay by credit card. Like every other business, the credit card companies charge us a fee every time a credit card is used - and we certainly have better ways to spend owner's money! I wonder how much of a problem it is? It is worth looking into.