I think you'll find that the missing games aren't recorded in your collection, I just checked that this is indeed the case with Sleichfahrt.
If you go to the game page and click Record Information that should do the trick you don't actually need to record any info. Alternatively open your collection list and add the games from there.
That was my first thought too... I once had the same problem and read somewhere the problem could be solved that way. And it was.
But Christopher seems to own none of the games in his hotlist. It's weird that 3 of them are displayed by the widget while the others don't.