Apple will not be able to fix a problem with your WhatsApp contacts. WhatsApp has struggled to provide a stable version of their software and have tried 11 times in the last month with updates. When importing WhatsApp contacts, it is that app that provides the information to import. WhatsApp has had the iOS 18 beta for 3 months to test their service, so they have had the opportunity to make sure it is working correctly. Hopefully they will start testing their updates thoroughly before releasing them instead of relying on their users to be bug testers. It has been this way ever since Meta purchased them where their focus changed from being a privacy centric messaging app to one now that harvests their users personal information to sell to advertisers. That is Meta's business model and how they report revenue from an app without selling a product.