The following error says I should report this to the DataNucleus developers so just doing my duty :)
I do have some classes with 'int' attributes - when creating the schema from scratch these map to bigint(20) - with both old and new connector versions.
<discriminator strategy="value-map" indexed="true" value="86284453">
<column name="classid" jdbc-type="INTEGER" />
and these are mapped to int(11) with both old and new connector versions.