Ideally, there would have been written agreement to a payment plan, which, if adhered to, would avoid any penalties aside from interest on the remaining debt at any particular time. Given the circumstances (knowledge of the owner’s disability and their regular payments), it seems unreasonable to have proceeded to debt collection rather than treating the owner like someone with an agreed payment plan.
I would try bypassing the strata manager and talk to the committee. I would also write to explain why the additional fees and debt collection costs should be waived.