Try just using "Recent" and close the app or click on the trash icon to close all apps.
What app, always same?
Clear app cache after Force Stop.
Clean setup? That always help.
Next, try clearing system cache.
What were you using before? Did it have 7.0?
Possibly using an app not fully compliant.
I find it fast, and setup with downloading dozens of apps very very quick, but sometimes an app will go Wong and need to be uninstalled and reinstalled.
Still, shouldn't be happening. A couple people, myself included, had to do reset. For some reason the factory installed OS wasn't right.