My app needs a reference to the SCNSceneRenderer for hit testing. I thus use SCNSceneRenderer delegate to get and store the reference as property in my ViewModel:

@MainActor
@Observable
final class ViewModel: NSObject, @preconcurrency SCNSceneRendererDelegate {
    private(set) weak var renderer: (any SCNSceneRenderer)?
//…
    
    func renderer(_ renderer: any SCNSceneRenderer, updateAtTime time: TimeInterval) {
        self.renderer = renderer
    }
}  

With this code, I get in func renderer the warning:

warning: data race detected: @MainActor function at
…/ViewModel.swift:10 was not called on the main thread

As a bug fix, I changed func renderer to:

func renderer(_ renderer: any SCNSceneRenderer, updateAtTime time: TimeInterval) {
    Task {
        await MainActor.run {
            self.renderer = renderer
        }
    }
}

Now, the warning within func renderer is gone. However, the Issue Navigator shows the following error:

warning: data race detected: @MainActor function at
…/ViewModel.swift:1023 was not called on the main thread

Line 1023 is the line where func renderer is defined.

My question is:
How can there be a data race, when the ViewModel is @MainActor, and the body of the function is executed on the MainActor? And how could I fix the bug?