We've also faced this assertion recently
Assertion failure in -[PHPickerViewController _handleRemoteViewControllerConnection:extension:extensionRequestIdentifier:error:completionHandler:], /Library/Caches/com.apple.xbs/Sources/Photos_UI/Projects/PhotosUI/PhotosUI/macOS+iOS/PHPicker/PHPicker.m:1489 [extension _extensionContextForUUID:PFAssertClass(extensionRequestIdentifier, NSUUID)] should be an instance inheriting from PUPickerExtensionHostContext, but it is nil
If someone has knows what this might indicate, or whether this is a bug in the framework please reply