Tristana E passive doesn't do damage with energized shot (sometimes)

I tried recreating this bug and it seems to only happen sometimes. It's hard to tell what the exact scenario is in which this bug occurs. But start farming in a practice game/practice tool with any energized item, and occasionally if you last hit a minion with an energized shot, the passive from the E where it damages surrounding minions won't work.

This bug has heavy impact because it randomly slows your wave clear down, making you take up more time wave clearing than you initially planned on.

Here is video: https://streamable.com/eo6j1

Happens at 8 seconds.