Prior to update (20.4.0), we observed the data_engine probe periodic hang ups. It would stop forwarding queue messages and become 'yellow' in the Hub status.
After installing the update, which went very smooth, the data_engine hang ups became much more frequent. The probe currently hangs like this multiple times per day, once every few hours.
I attached data_engine log taken during the hung state.
Release : 20.4
and make sure you are using the correct version of Oracle Instant Client.