On the simulation dialog in the "Display" tab, scroll down to the "View" group and there is an option called "Viewpoint". You can select "Machine base", "Model", or "Tool" to control which thing is held fixed on the screen.
You are simulating with "Viewpoint" = "Model". That's useful for when you are zoomed in on the model. You probably also want "Machine | Show base" turned off for this.
For what you are doing, I think you want "Machine base". This is better for when you are zoomed out and looking at the whole machine.
This menu picked up a new option in the latest release. That's probably why the behavior has just changed for you.

Brek Miller
Software Engineer