ODBC message "server closed the connection unexpectedly" when accessing a PG/11.3 DB

We are using MS-Access as a front-end to work with tables served by
a Postrges/11.3 DB on linux as the MS-Access backend through ODBC. I have
my users install on their Windows laptops a PG driver for ODBC from here...
https://www.postgresql.org/ftp/odbc/versions/msi and selecting
psqlodbc-12_02_0000.zip. This setup seems to work fine for me. However...

I have a user who got a "server closed the connection unexpectedly" after
trying the "Test Connection" feature in ODBC. The "server closed the
connection". Hmmmmm.... . Is this saying that the user was connected, then
the connection was closed ?

I'm not the DB Admin but I had them give me the contents of the instance
log for the time period in question. There's nothing in there that would
indicate that the server closed a connection.

This user is on the other side of the world and there's a possibility that
a firewall is in play. But I wouldn't expect to see a closed connection
error for something like that. More like a message saying that it couldn't
make the connection in the first place.

I asked the user to recreate the error while running the Tracing facility
in ODBC, then send me the logs. But in the meantime, has anyone heard of
problems like this using ODBC (on Windows if that matters) ?

Thanks in Advance !