Intermittently (and I have yet to determine a reliable way to duplicate it), when selecting a different item on my hotbar, the selection on the hotbar will correctly outline the intended item, but the actual held item doesn’t change.  The result ranges from mildly annoying (when building and changing blocks) to deadly (when building and suddenly attacked, and needing the selected sword to actually be present instead of bashing the mob with a building block).

Screenshots show the result of this bug. I am still searching for a reliable means of triggering the bug.