Steps: (1) Go to URL. The page demo's combinations of Flexbox properties. (2) Click the "Sizing & Direction" tab (3) Change "align-items" to "stretch" (4) Change "align-items" back to "center" (5) Change "flex-direction" to either of the "column" options (6) Change "flex-direction" back to "row" The bug is apparent at step #4, where the flexbox items do not render as center-aligned along the vertical axis. Steps #5-6 establish that you can re-display the proper flexbox behavior only after changing the overall direction.
The relevant website no longer exists.