IT is a good idea to clean out that venting/ductwork every few years. Now that you suspect lint leakage, it would be a good idea to do it soon. House fires begin from lint-clogged venting.

Look down at the bottom of the lint screen holder and check for buildup or objects preventing the screen from seating properly and allowing lint to slip under or around it.
One would think if there is enough to coat both sides then a larger amount is getting past and clogging the vent hose and outlet too.