I use two difference devices EDGE530 for cycling and Vivoactive 4 for the other activities.
In the daily summary, there is a gap in HR graph, as i didn't have the watches on my wrist, but was using the E530 with the HR sensor on the brust.
Why the HR graph is not filled by the data from the activity, while cycling. These data are also missing in the "Intensive activity" weekly summary 
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Note: both devices have activated the TrueUp function.