My galaxy 4 watch is now having problems with sleep tracking after the last update. If I have 2 sleep cycles when I get up in the middle of the night it only records the newest cycle. I tried resetting my watch and it worked for a few days and now the problem is back.
It's because it's not one continuous sleep cycle. You have one sleep cycle on the previous day and one sleep cycle on the current day. That's why you have to tap on each to get the totals for each different sleep cycle.
The first sleep cycle showed 0 rem 0 deep sleep. I know it didn't work right since I was dreaming and 5 hours with nothing. It did take O2 levels during my 5 hours. There also was only a 10 minute gap between sleep cycles.