As a player was booked with yellow card, I made substitution instruction as soon as possible. However, before the substitute was effective, my player was directly ejected with a red card. Afterwards, this substitution was counted, but my team only had 10 players on field.
So, the bug is, substitution was counted, even if it did not really happened because the player to be substituted out was ejected.
I just it should not be rare and may be reported before.