This is happen to me too
Sensors like wrist wake up, heart rate monitoring etc are not working after the latest update.
I also did multiple watch reset, factory reset, cleared both gear app & plugins data.
However, my friend's watch is working even after this update, we bought it together. So, it happened to few unlucky ones only.
The only difference between our watch is MCU version (checked using test mode, sensor hub, *#0*#):
My MCU version is BR010 (Status: Fail) where as his MCU version is BR0118032200 (Status: Pass).
I think this is the probable cause, may be my update was not applied well or fully since we have exact same watch brought from same place at same time.
Hope next update will fix it.
Tizen version: 188.8.131.52
Software version: R760XXU2CRG3