There are printers with papersources unknown to Qt. In pre 5.3 Releases it was possible to preset a paper source with a id which was not known to Qt. In 5.3. this is not possible any more.
Qt pre 5.3 tried to match the given paper sources against the known qt paper source ids. If found it translated the Qt id to the Windows id. If not found Qt used the given paper source 1:1 without translation.
Qt 5.3 ignores all paper source ids >= 14 and sets Auto instead.

My printer is a Canon iR-ADV C5235. It has the paper sources: Einzug 1, Einzug 2, Einzug 3, Einzug 4. With Qt 5.3 it is not possible, to use 'Einzug 4' because it has a Windows id of 264.

Suggestion: implement setPaperSource() / paperSource() with an optional additional parameter which indicates that it should use the native ID's.