My phone is the xperia-xa2. After updating to 4.3.0,12 it worked fine. But after a while, it was not able to reach the cellular network anymore. It may have to do with this:
Upgrading to 4.3: How/why to remove the “ofono-alien-binder-plugin” package?
This tricks did not work for me:
Resetting oFono settings to make mobile data work
This is the only solution I found:
Reverting Xperia device to Android OS and reinstalling Sailfish OS
If somebody knows an easier way, I would like to read about it.