I am getting the following exception:
Caused by: org.postgresql.util.PSQLException: ERROR: character 0xefbfbd of encoding \"UTF8\" has no equivalent in \"WIN
I had a very similar issue. I had a linked server from SQL Server to a PostgreSQL database. Some data I had in the table I was selecting from using an openquery statement had some character that didn't have an equivalent in Win1252. The problem was that the System DSN entry (to be found under the ODBC Data Source Administrator) I had used for the connection was configured to use PostgreSQL ANSI(x64) rather than PostgreSQL Unicode(x64). Creating a new data source with the Unicode support and creating a new modified linked server and refernecing the new linked server in your openquery resolved the issue for me. Happy days.