I had a NSA250 now I have a TZ400. All current.
Firmware Version: SonicOS Enhanced 6.2.7.1-23n
Safemode Version: SafeMode 6.2.3.9
ROM Version: SonicROM 5.6.2.1
Netpath will NOT work unless these 3 things are UNCHECKED...
- Enable Stealth Mode
- Randomize IP ID
- Decrement IP TTL for forwarded traffic
See pic...

BUUUT... I do NOT know the risk(s) of leaving them unchecked.
Test it and you will see. Sonicwall NOR Solarwinds can fix this and I have case numbers to prove it. Had we known this before we dropped $10k on Solarwinds...
Meh!