Incident
We have upgraded our WhatsAppp API gateway from v2.37.1 (expiring 29 March) to v2.39.3 on Saturday, few hours after the upgrade, few clients complaining cannot receive/send messages probably
Root cause
We found out that it's mostly due to a bug introduced in the new version v2.39.3 which just released 25 March.
Resolution
We have downgraded the API clients to v.2.39.2 yesterday afternoon and cannot find any issues after that from our server logs (but v2.39.2 has some bugs too according to the change log)