I'd really suspect a classloading issue here. TS gets connection through JNDI and then tries to unwrap/cast. By any chance, have you got two postgresql driver jars in different classloaders (e.g. two webapps or tomcat lib and webapp or tomcat common lib)?
Caused by: java.lang.ClassCastException: org.apache.tomcat.dbcp.dbcp2.PoolingDataSource$PoolGuardConnectionWrapper cannot be cast to org.postgresql.PGConnection