As a last resort I deleted and redownloaded the game on the PS4. Deleted all the my saves too since I just started Act I. As a safety precaution I went back to the classic way of making multiple characters and just keeping important items in the Personal Stashes.
As a test I placed basic equipment in the Shared Stashes just to see if they’ll disappear if I turn off the console and restart after a while. Now so far items I placed were still there. But I’m still not relaxed as there’s no new patch yet.
Still cautious of Shared Stashes in the game that I move items between all the my characters’ Personal Stashes and making sure items I leave in the Shared Stashes are those I won’t miss. I made it a point not to leave any gems and skulls in the Shared Stashes. This is all as of Act III by the way.