This behavior can only occur in Circuit Mode. The login to the Smart Flex device has taken place during the first training phase (orange) or the break on the device (yellow). Therefore, only one set is documented because both training phases were not trained.
In order for both sets to be documented, the logon to the Smart Flex device must occur during the pause (blue) phase.
Please aslo had a look to our Article: What do blue lights mean on EGYM Smart Flex?