ODBC Linked Server - AS/400 data truncated in SQL Server but fine in MS Query

We have an AS/400 DB which we connect to using a 64-bit ODBC driver.  If i connect to the ODBC driver using Excel's Microsoft Query data returns fine.

If however I run the same query in SQL Server 2012 with the ODBC referenced as a linked server using the MS OLE DB Provider for ODBC Drivers the data is wrong  Specifically the decimals types have the decimal portions truncated (so 17.45 is returned as 17.00).

A possibly clue to this is I am having to run the SQL in an OPENQUERY as I receive an error regarding metadata.  As am example, the following runs fine:

Select * from OPENQUERY(test2, 'Select UnitCost from oslines')

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But this statement gives an error:

Select UnitCost from test2.mnprod..oslines

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The error is:

The OLE DB provider "MSDASQL" for linked server "test2" supplied inconsistent metadata for a column. The column "LineNo" (compile-time ordinal 2) of object ""mnprod"."oslines"" was reported to have a "DBTYPE" of 2 at compile time and 18 at run time.