One of the bugs... er, "undocumented features", of this beta is the occasional app drawer arranging the icons in a seemingly random order. Closing & reopening does not resolve it. I submitted an error report on it.
I have found that restarting the phone does put it back in the order I want it (which is alphabetical). Try it and see if it helps you.
It's not undocumented this is one of the first error reports I created The second day the beta was released. In the meantime till beta 2 update. Swipe up to get to the app drawer, press the three dots in the upper right hand corner choose sort, and switch it to alphabetical or custom then back to prefer sort order. No reboot required.
I used the term jokingly. I didn't imply it was "unreported"... the term "undocumented feature" in that it's not something that Samsung planned. Switching from custom order to alphabetical may work for you, but not for me.
