I don't find the slide carrier on the V500 that flimsy, considering the simple task it has. For color negatives, though, all the snapping in and out is more tedious.
The V500 comes with a separate negative holder for 2 1/4 negatives.
I've found it an adequate performer overall for the task at hand. I too find it odd that one slide/neg has preserved its colour well, while the adjacent one might be faded beyond salvage.