Sejuani's E doesn't consistently stun Scuttle Crab

In a matchmaking game, try to E Scuttle Crab at 4 stacks with Sejuani and occasionally all stacks get consumed but the stun doesn't apply. You can then re-apply stun stacks starting from 0. This happens to every other Scuttle Crab for me. However, it seems that this bug can't be recreated in practice mode.

It is not caused by Scuttle Crab moving away from line-of-sight because I have vision on her all the time. It might be caused by mashing E or autoattack before the 4th stack is applied but I can't successfully recreate it in practice mode.

This bug has been existing since July at least.

Also can we please have a language selection feature for the new client? For some foreign clients they don't sort champions alphabetically and recently I had to dodge a game because I couldn't find or search the champion I want to play. It is not too big of a problem but I would be very grateful if I can search champions with English in other regions.