The issue with the window stickers is still going on. For whatever reason, there have been very few new window stickers for the last couple of weeks. There have been none since June 12. It seems plausible that this is related to a parts supply issue, either related to the seat belt recall or something else. Other data sources make it seem like cars are still going down the assembly line and being built, but the lack of window stickers typically is a sign that none are being invoiced and shipped to dealers/customers. This appears to be an issue specific to Corvettes and not all GM vehicles.
I'll post another update when the window stickers have started working again. For now, the site will keep on checking and hopefully things return to normal soon.