Tracker Loses Data, Great While Working – Gravitus - Workout Tracker Review

I have been using the tracker for a week at the gym. Out of my 6 workouts, I have lost the data on 2. This appears to happen when I leave the app running in the background while switching to other apps on my phone. Is this something I can solve myself, or maybe an issue that occurs when switching from WiFi to data?
Review by brandopopop on Gravitus - Workout Tracker.