6x pro optical HR sensor, altimeter and barometer stopped working

Hi all, i'm looking to see if any other community members have had similar issues before I contact Garmin support. 

I have a 3 month old Fenix 6X Pro, i have been using it successfully for the last few months marathon training. At some point during yesterdays run, the optical HR sensor and a number of other features stopped working. Note I was, and always do, use an external HR strap, I noticed because the alt was showing as zero incorrectly. Once my run had finished and not in an activity mode i noticed the following.

  • No pulse OX reading
  • No wrist HR reading
  • No stress score (error message 'check fit'
  • No body battery score
  • No breath rate measure
  • My run had no vertical measured, a hilly run showed 0m gain
  • Current alt showing as 0
  • Barro currently showing 0
  • Calibrating the altimeter failed with an error
  • Calibrating the barometer failed with an error 
  • Using the broadcast HR feature shows --
  • No lights coming from the optical sensor on the back of the watch

Things i've checked and tried

  • Reboot
  • Battery saver is not on
  • Wrist HR status = auto
  • Charge fully and reboot
  • Plugged into Garmin express and checked the software was up to date, it was. Currently running v9.00 (258033d) and i checked the sensor hub version is 5.07
  • Factory reset 'Reset default settings'
  • Factory reset 'Delete data and reset settings'
  • Set up a new power mode and tried an activity with it
  • I can still connect an external HR strap and that works

Does anyone have any other suggestions of what to try or any similar experiences? I had noticed lots of forum posts from about 9 months ago with wrist HR issues but that was with version 2.3 approximately. 

Many thanks in advance for any suggestions.