I had mine replaced by the dealer last Sept. while the 5er was in for a list of repairs. That end piece's main function isn't to stop bugs from getting in. "Some newer models have the drain hose protruding through the access door with a small cap inserted into the end of the drain hose. This cap has many small holes.
This drain tube needs to have a āPā trap before exiting the lower access panel. Condensation drains are designed to allow condensation to escape and prevent ambient air from reaching the cooling fins."