I have really only heard about this happening with the very cheap aftermarket suppliers and some other problems with the vinyl being too thin, ripping easily on installation even on vinyl side-and-back/leather facsia upholstery. V-B had dropped selling a budget vinyl seat upholstery kit a while ago, and, having seen a few, I suspect it was for that reason.
At this point, V-B might still be agreeable to looking at and/or helping you with the problem, especially if they've had a few compaints. Like most of the components sold by the various catalogs, leather seats are done by contractors and there are many out there bidding the business. A bad batch or supplier order can always occur and it could ruin the catalog's and supplier's reputations if not properly addressed. I would expect most suppliers of premium components to test the dyes for colorfastness and wear characteristics themselves, but this can get very expensive.
If no help is forthcoming and you want to save your seats, you may want to have them professionally refinished. This too can be expensive, but will be less costly than replacement, especially if they do the repairs with the covers on the frames.
Another alternative is that SEM and Duplicolor make speialty spray finishes for upholstery that I have used on both vinyl and leather that holds up very well to wear, if done correctly. The key, like all paint, is preparation. I tended to clean everything with laquer thinner first, often removing the original finish immediately prior to painting and then did this on a warm day in the most dust-free enviroment I could find. The results were pretty good and it worked better on leather than vinyl because of the porousity of the hides.
I hope that helps you. Good luck and keep us posted on what happens.
Art