Hello Smilefhm,
Since this issue is occurring only with WhatsApp, and since you've already worked with Apple Support, we recommend reaching out to the app developer directly. They may have additional information specific to their app. Here's how: How to contact an app developer
"Contact the developer of an iOS, iPadOS, or watchOS app
- Open the App Store on your iPhone or iPad.
- Search for the app, then tap it. If you can't find it, tap the account button or your photo at the top of the screen, tap Purchased, tap "Not on this [device]," then tap the app.
- The app's product page appears. Scroll to the Ratings & Reviews section, then tap App Support. If you don't see App Support, make sure that you're signed in with the correct Apple ID."
Take care!