When I add apps and push them down to the Samsung Tab A they install fine then randomly in the managed apps screen they disapear and reinstall . Its not all apps but a few I have noticed is google maps , samsung email , chrome
all apps were downloaded from the play store.
I also will remove any internet shortcuts on the home screen.
After I spending some time on this I decided not to use Knox. I set my devices as the owner and use a Block List. I find that I can block all the other garbage that is loaded from the device. Once you set up a block list all system apps and preloaded apps are allowed to run. I use a android app called package names to get the item names to block and put them the block list. That will stop all the items you don't want or don't need from loading. Then what ever apps I want them to have other than the system apps I just add them from the playstore on the manage apps screen