I have been having all of the following issue. The good news is that I am working with an Apple Support Specialist and they called me back yesterday asking to pull logs from my iPhone.
It seems that Apple is not only 'aware' of the issue, but they have developers assigned to the investigation.
1) Some workouts not syncing to Fitness App
2) Heart Rate Data has large gaps
3) Map missing from workout PRIOR to the update
4) Map only showing starting position on sync'd workouts POST update
5) Activity Bar Timeline not showing all data (Easily seen with the stand timeline)
6) Data MANUALLY sync'd from iPhone to Strava is only showing about 60% of the distance