I have also been having the same issue. I have smart lock set to keep my phone unlocked when I'm paired with my Galaxy Watch or my car's bluetooth, and also when I'm at a certain location like my house or work. I've noticed it does eventually lock itself regardless after a certain period of inactivity which is normal, but since the latest update came out I've noticed it does it seemingly at random. The only work around I've found for this so far is to remove my watch and car from the list of trusted devices and re-add them however; this is a temporary fix as it seems to go right back to doing it after about a day. Hopefully Samsung can get this patched soon because it is really inconveniencing.
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