Can you post a link to the activity you are referring to?  It might help if we can see that so we can see if there is something obvious happening.  Also, what does your watch say for the activity pace and related information?

Hey @nmkenny1, 
Just following up on this one. These data discrepancies could be due to the way Samsung Health is analyzing the data.
 
For example, consider the process of determining how much resting vs moving time is in an activity. What constitutes a rest? Is it when you're at rest for 1, 3, 10, or 20 seconds? And what does your speed have to fall below in order for you to be considered at rest? 1 second might capture too many false positives and 20 seconds may be too strict. One calculation isn't necessarily correct or incorrect, but we do feel we're using standards that most athletes would agree upon.
 
We understand our athletes use hundreds of different devices and apps and are doing our best to accurately analyze each file. We're always working to improve our athletes' experience and we will pass this feedback along to our engineering teams.

If you want our team to take a closer look at your activities, please submit a support ticket and they'll take a look.