I’m trying to look for it, but having trouble finding it.

I vaguely want to say that it was also maybe related to having pending downloads. It was like if you were playing a non-steam game, the sleep process would trigger the deck to start downloading again, interrupting the sleep. Once sleep was interrupted the game would start running again and downloads would be paused, making it seem like the deck failed to sleep for no reason. If you didn’t have any downloads pending, the deck would go to sleep fine even in a 3rd party game. Unfortunately the deck frequently has a couple mini-updates available whenever you close a game, so this bug happened pretty often.