Still occurring with 5.0.0.29.
Behavior is a bit different, though, acknowledging the alarm works fine. But it’s still silent. (I’m not completely sure it occurred, because it did even not show up as missed alarm). I also checked that it did not work with timers.
In case it’s relevant, the lag due to vibration seems to have been fixed (there is no longer a lag), but the phone still does not vibrate.