I've seen this happen on my A50 also. I changed my SmartLock settings to not unlock while the phone is on me, and that seemed to help, but seems to still happen occassionally. My SmartLock also does not recognize my home location to keep the phone unlocked. Hoping Samsung can fix this soon!
Try disabling wake gestures like tap to wake, and enable prevent accidental touches (if these are present). Then see if the issue persists.