AppTaskWorker - Running class methods at sporadic intervals
Start() is spawning an infinite number of new tasks without waiting for them to complete. It's also a bit weird that Start() is blocking the calling thread.

Make Start() async and await the Task returned by Task.Run.

Start(), a blocking method, being called at the end of the constructor is an absolute no-go. The constructor is not done, the object initialization is never completed.



Unless you're living on UTC (DateTime.Now - lastProcessed).TotalSeconds is going to be inconsistent around daylight saving transitions.