I ran into a bug some days ago, when Oblivitron failed to summon the Shifting Chameleon (from the Pet Training hunter hero power during Dalaran Heist) that was changed into a Clockwork Gnome at the time. I have a screenshot, but I can’t post it.
Known but as of yet unacknowledged bug with Oblivitron. Its Deathrattle checks if the board is full as a queuing condition, not a trigger condition. That means the minions get counted before the dying Oblivitron has been removed the board. Your screenshot shows 6 other minions were in play with it when it died, so it counted itself and thought the board was full.
https://github.com/HearthSim/hs-bugs/issues/1204