I have this problem as well. The clips that hold the plastic ring in place broke in the process of opening and closing the canister. I have just spoken to Dyson support. The closest thing to the part available for purchase on their website is this: https://www.dyson.com/support/journey/spare-details.971455-01. They informed me that the entire canister needs to be replaced at a cost of 30$ plus shipping--not worth it for such a small part. Images below for reference.
[image|3622571]
[image|3622570]