What would cause my barely used green bearing to do this?

TurboGLH said

Again, that bit about ball bearings and bad axial loading is just plain wrong, ball bearings have EXCELLENT axial load capacity. They're used extensively in aerospace for exactly that function, to control axial movement in conjunction with rollers for radial control.

Click to expand...

Um, no.
"If the bearing needs to cope with a heavy axial load, an angular contact bearing should be used. These have a different internal design allowing them to handle much greater axial loads than standard radial ball bearings."
SMB Bearings

Back to the drawing (conclusions) board for you!

If you want to cite aerospace applications, go right ahead. I won't wait.