You can try a couple of things:
- Go to Settings & Search for "Reset" & Reset your Network Settings.
- Boot into Recovery & Wipe Cache.
One of those should resolve the issue for you.
Pretty sure that if there was a "bug", tens of thousands of people would be reporting the same issue.
Regarding your Network issue, open the Samsung Members app & Click on Support, run the Diagnostics for the SIM card & see if you get any error messages.
SIM cards can & do fail.
You could also just pop the SIM card out & Reinsert the SIM.
See if that helps.
Instructions on how to Wipe Cache: