RAP - RDF API for PHP

I cannot make uniting models from database work very reliably with SPARQL.
E.g.

$TestModel1 = $TestDatabase->getModel("test1");
$TestModel2 = $TestDatabase->getModel("test2");

$TestModel3 = $TestModel1->unite($TestModel2);

Both $TestModel1 and $TestModel2 work fine separately and I can query them
with SPARQL. I can also see these models in SQL table when I query the
statements.

Now, if I query $TestModel3 with SPARQL it seems that I may get some good
information, but also a lot of crap. It gives more resources than it should
for my queries and also some of the resource property info seems to be
mixed up.

If I look $TestModel3 as a table with
$TestModel3->writeAsHtmlTable();
it looks fine but I did not check the URIs so maybe it is not.