Felt like I should post this video after finding others with the same problem. See this video for the overall disassembly. • Taking apart a Dyson DC39 Triggerhead - be... , the user notes that Dyson replaced his, so maybe try them first. I had already torn into it to find the problem, so attempted a repair. After a month of use it works better than it ever has, so yay me. Apologies for the rambling, mumbling and poor editing.
I created this video with the YouTube Video Editor ( / editor )