On AT&T S8+ running Oreo I'm running into an issue where the navbar appears when I swipe up to go home. This issue maybe caused by using several apps in conjunction with Navigation Gestures by XDA. I have Shortcutter Quick Settings & Side bar still installed on my phone with access to Secure Settings thru ADB, this is the app I normally use for immersive mode. Even with immersive mode turned off I still get this issue, not sure if I need to revoke secure settings access and possibly uninstall app (will test and report back later). I also noticed an issue where I changed the height of the pill and it changed the size of the letters on my screen, but not the whole UI, so I don't think its a DPI issue.
Edit: Was not able to recreate the font size issue.
Update: I have found another issue where the pill disappears and I'm not able to navigate from this post without using the softkey edge app