EDIT: Can confirm the update just fixed this, thanks for the quick fix!
Since the last update, I can’t back out of the Post screen using hardware or in-app back buttons. The only way to back out is to first type something then hit back, which triggers the Stay/Leave popup. Before picking either option it already backs out of and discards the post, then choosing Leave backs out one more screen. Picking Stay does nothing.
Just checked the Play Store and found an update for Connect, can confirm it resolves my issue of needing to double tap the back button.