Don’t think so.
- Re-digest the info links in post #2
- Reset the SPA112 to Factory settings, Quick setup, …
- stick to defaults and keep changes as minimal as possible
- Voice / Line 1/2 :
NAT Keep Alive Enable: no → yes - Voice / SIP :
NAT Keep Alive Intvl: 15 → 5
Redirect Keep Alive: no → yes
Sorry for the moment - it’s long past midnight (MEST) over here.