I'm still waiting the Virtual Partner in my FR235...
However, it looks like the data between 2nd and 19th may are definitively lost as they don't show up in the graphs.
As DASHER11 has indicated there was a fix for this issue released to Garmin Connect this morning. Any new activities uploaded will show this the average stride length. Any activity where this information is missing can be exported and then re-uploaded to Garmin Connect. We do apologize for any inconvenience that this caused.