I've got several PS3 engines. I also run conventional with Z-1000s. I've noticed that on several of my steam engines, as they run, the volume has automatically dropped. It is usually a good drop in volume as well. I had one, while it ran with the potentiometer set at 1/2 dropped to about a 1/4 volume level then silent as it chugged around. Shut down and restart fixed it. I've seen it on many PS3 engines.
Is this a known issue and is there a fix?