Do you have a Walker AirSep? We do on our 6bta and I have experienced the same. Our "solution" was to use the Walker sealing compound between the filter and the sleeve, two T type hose clamps and not to over tighten. If you over tighten you can collapse a section of the sleeve (I did). Still, you have to be careful not to hit the filter arrangement as you move around it. As I recall, that sleeve is slightly tapered, which may aid in getting the assembly onto the sleeve but makes it so it has a tendency to work itself off.
Deer Isle, Maine