GW BX5600 - Atomic time sync - RCVD indicator

It's not clear in the instructions (yes I've combed through each section 5 times) how the atomic time sync works, in particular the RCVD indicator on the timekeeping screen.

I performed a manual time sync yesterday evening and the RCVD indicator permanently appeared as expected. I left the watch by my window in the 12 o'clock position overnight, only to wake up to find the RCVD has disappeared. According to the instructions this means the atomic time sync was not successful.

My classic square right next to it updated. I hate how the newer models do not allow you to see the date and time stamp of the last atomic time stamp. This isn't an issue on my GW-M5610U-1ER, atomic time sync works flawlessly and more importantly I can sanity check the date and time of the last time sync by simply pressing the D button once.

Is my new BX5600 faulty?