Glad I’m not alone. 12.9” 2018 iPad Pro. Same deal, since upgrading to iPadOS 13, when I unlock after waking, the orientation reverts to something other than the orientation its actually in. Additionally, when I launch certain apps, the orientation also freaks out, crops the screen or does stupid stuff.
i keep hoping it will improve with an update, but no changes with 13.1, 13.2, 13.2.2. I wish they’d fix this.