When uploading a new build for an app in Testflighty

Dear Developer,

We identified one or more issues with a recent delivery for your app, “Maxim Fitness” 1.1 (30). Please correct the following issues, then upload again.

**ITMS-90809: Deprecated API Usage** - New apps that use UIWebView are no longer accepted. Instead, use WKWebView for improved security and reliability. Learn more (https://developer.apple.com/documentation/uikit/uiwebview).

Best regards,

The App Store Team

We have gotten this error multiple times when uploading to the appstore.
We tried using Grep to identify the issue and remove it.
What other things can we try?