I used Karn on the left node in this past weekend’s HoD (Samut).
I never lost a creature; however, my creature count was always 2 out of 3.
Luckily it never reached 3.
Seems that Karns first ability was dumping the unneeded creatures into Exile and they were being counted as lost.
@BlessedOne
I’d recommend sending a ticket to Customer Support so they can investigate this issue.
I saw this as well.