devtrackers.gg
Can you PM me your ally code and the date and time this happened, please, so that we can have a look? Thanks!
Not sure if this helps, but it seems to be happening a in this TB when Han stuns someone vs a GG wave 4. There have been a bunch of posts about it in the past few days.
That was our first assumption as well but after extensive testing that doesn't seem to be the cause.