Had this problem on my XA2 for at least one year. I could reboot (once was enough for me) or I could restart adsprpcd (with qCommand it took me a couple of seconds). This happened at least once a month on my phone.
However, had to revert to Android with Emma and then reflash latest 4.4 version of SFOS about two months ago. This looks like it has cured it for me. Hope it helps others too!
P.S. This time I’ve flashed over Android 9. Previously, I’ve flashed over Android 8. Using the recommended firmware both times.