Try handling unclosed sql connections by calling dispose on the engine before it is put back into the pool.

cdplib/db_handlers/SQLHandler.py

@@ -505,7 +505,7 @@ class SQLHandler:
             #connection = self._engine.connect()
 
             data = pd.read_sql(sql=query,
-                               con=self._engines,
+                               con=self._engine,
                                **read_sql_kwargs)
 
             #connection.close()