When I have the game running in the background, it often crashes (causing me to lose out on progress). It seems to do it when I have it running in the background for more than a few hours.
For example, I just returned from a convention where my FitBit reports having walked just over 5.5k steps over the span of 3 hours. However, when I opened the game up from the minimized state, it went through the launch process (with the loading bar) and it had only tracked 1.1k of those steps (so it had crashed somewhere during the convention).
I don’t always wear my FitBit, but I always have my phone with me (so using the in-game step counter is more reliable…except for when the game crashes and I lose any progress that I would have made).