ORA Error 12637 - Packet receive failed

Hi, I am receiving this error only while trying to connect to a database via TOAD.
Can connect via SQL*Plus and SQL Developer.
The recent change was the DB got upgraded from 12.1.1 to 12.1.2. Since then I am unable to connect over VPN. Was able to connect over the VPN prior to upgrade. Yet to try over LAN.
Using TOAD for Oracle
Pls advise.

Thank you.

Exact same scenario for me. Any insight?

There is an issue with configured Firewall (developer is passing while toad is not)
Toad has nothing with this error.