The pen that refused to be finished....

Hey everyone, I have been having some issues turning a Churchill roller-ball. The cap section uses a drilled out 33/64" blank that any wood I use loves to just pop off at any moment during the final stages of turning.

I am using thick CA to glue the tube into the blank and doing my final adjustments using some very light cuts with a Spindlemaster.

Any ideas? I have blown through 3 cap blanks now....