Formatter places graphical square characters inside lines of code and does not format properly.
WORKAROUND:
The below setting may resolve the issue:
1. Select View | Preferences menu option
2. Select "General" under "Code Editors"
3. Check "Use TAB Characters" check box and hit OK
4. Re-format your code
STATUS:
Waiting for fix to be released in a future version of SQL Navigator for Oracle.