Fenix 6X PRO and HRM-Pro data offload with watch

If i finish an activity used a HRM-Pro ANT+ connected chest belt and afterwards use the menü in the watch to offload stored HR-Data - the fenix 6 processes, says okey und i can see activity in watch (with stats and running dynamics), but it produces a corrupt fit file which prevents syncing with connect - manually upload shows error in connect web portal.

if i clear protocoll from watch it is locked and cannot be removed... after starting an new activity you can delete it from the watch manually (no master reset required) - seems to be a bug ???

if i finish activity WITHOUT HRM Data offload from sensor the activity fit is okay and syncs - only happens if you use offline hrm from the watch menu ?

Is there a firmware which fix it ? I'd like to use offline data with hrm pro from watch ???