I have similari trouble but after applying the fix for phone call recordings. Have you sorted out without reset?
How to restore original hosts file?
I am pretty sure the modified hosts file is not affecting the core applications.
But
devel-su echo -e '0.0.0.0 localhost localhost.localdomain\n::1 localhost6 localhost6.localdomain6'
After some checks I found that a failed application of the official fix for the
Similar behaviour, native clock app.
Tabbed the app, animation to inform user: OK, I am starting… circle… nothing happens 
.
Restarted the phone. Multiple times 
. So far, no terminal or scripting involved.
Whatever happened, clock started again, one day or the other. I set an alarm, with repetitions (never did that before). Clock seems to be working fine again. At least, app starts immediately. Maybe this helps.
Running SF OS 4.3.0.12 on Sony Xperia XA2 + Android support. Using the native clock app from Jolla store.