Wow how disappointing for you. It sounds like the Property Manager isn't doing his/her job properly. The entire property should be inspected at routine inspections, not just the inside. Letting them get behind on rent repeatedly is unacceptable too. If I were in your shoes, I would address these concerns with the PM and request that the tenants be served a termination order on the grounds of unpaid rent. Then I would change agencies. Your paying your current agency to manage the lease on your property, and they just aren't up to scratch by the sounds of it.