Swift - Timer.publish(:) misfires

Question

I have a timer scheduled as following:

private var timerCancellable: Cancellable?

timerCancellable = Timer
        .publish(every: 1.0, on: .current, in: .common)
        .autoconnect()
        .scan(-1) { counter, _ in counter + 1 }
        .sink { counter in
            print("\(counter)")
            
        }

This works fine (print out 0 1 2 3 ...) when I test it on any normal view controller. But in a specific view controller which I a live camera feed with Metal shaders (and several different DispatchQueue instances), it gives this output:

0 0 1 2 3 ...

0 is repeated twice. I tried .main for RunLoop but the result is the same. Can anyone help?