While they are a pain in the butt, be aware if the discharge deflecter is missing or tied up AND an object whether it is a rock, can, stick or other object flies out from the mower and hurts or kills someone you can be held liable. Lawyers ( I call them buzzards as they are looking for a free meal) love these cases big bucks and big paychecks.
Those delectors though a pain are supposed to be designed to deflect objects down so the don't fly too far. Of course the manufacturer has the obligation to make a product that will last and not fall off, but the operator has the responsibility to not hit things and not break it off. (not saying you hit anything) .