HRV intervals failure on F7X (CIQ 11.28) and various devices inc Venu family

All my apps worked fine before 11.28 release on Fenix 7X. Reports of Venu 2 and S failing also. My code had been unchanged for about a year!!

https://forums.garmin.com/developer/connect-iq/f/discussion/326877/possible-venu-fenix7x-firmware-issue/1587037#1587037

https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/epix-2/325933/syncing-and-hrv-problems-with-11-28-update/1587684#1587684

https://forums.garmin.com/developer/connect-iq/f/discussion/326059/heart-intervals-broken-on-venu-firmware-update-and-now-other-devices?pifragment-1298=3#pifragment-1298=3

seems that Garmin HRV, sleep quality, training readiness and my apps are all affected. Heart rate intervals are sporadic or non-existant.

Regards,

David