With the release of V4 alpha 4, card-columns class truncates the top of the middle and right cards when the cards are of varying heights. The same behavior occurs on the bottom edge, although it appears to be the third column that is shown completely, with 1 and 2 being cut off.

Browser? Also, are you using CSS columns?
I'm seeing the same behavior, and also seeing it on the Bootstrap documentation site. I'm on Mac OS X Chrome beta channel (currently 53.0.2785.80 beta (64-bit)).

I tested in IE 11, Firefox, Chrome on Windows 7. All the same. I'm just using the bootstrap.js and bootstrap.css from the dist folder, so whatever the default settings are.
Likely something to do with the display: block change we introduced in Alpha 4.

Captured in official documentation
I have tried! Fixed!!
Thanks!
Most helpful comment
Captured in official documentation