This is still not fixed on the May 2019 update, G970U1UES1ASDB. I guarantee this is related to the accidental touch protection not working either. The proximity sensor is not being used when the screen is off which is the problem and what is causing these features to not work. Never had this problem on my S9. Regret getting the S10.
Galaxy s8-the "accidental touch" "smart stay" and "always on display" features have not functioned correctly for an extended time. I frequently have trouble ending calls using speaker phone because the screen glitches off/on. I've been given the explanation to disable "smart stay", after doing so, problem still occurs. And I certainly don't understand what the "accidental touch" feature is supposed to accomplish, that a screen lock doesn't prevent. I would honestly love a description of its uses.