Ever had a DCI quick switch bottle that was hard to put on?  If you have or if you ever run into it you may want to check the bottle adapter.
The symptom that will be reported to you will be that the office has a really hard time when trying to push the bottle onto the male adapter.  Frequently it is noticed after they purchase a new bottle or right after they convert to te quick switch style adapter.  The cause is over tightening the adapter onto the bottle.  Overtightening the adapter causes the flange inside to distort and contact the bottom of the male adapter.  Often time it will also have air leaks when they do finally wrestle it on due to the flange breaking away slightly for the excess force.
Attached is a cross sectioned adapter that had been over tightened.