I guess you’re on a mac or iOS device. It would be helpful to know the OS version and platform (intel or arm). Do you have any third-party audio interface connected? When you open the audio settings window in the AudioPluginHost, how are the input and output devices configured? A screenshot of this window might help.
When you say that you added a new audio input, do you mean in addition to the audio input/output and midi input/output nodes that are created by default, or are you deleting those and starting from a completely blank project?
Crashes in the AudioPluginHost are most frequently caused by plugins that have been loaded into the graph. Are you certain that there are no plugin nodes in the saved graph?
Finally, please share the full stack trace at the point of the crash. If the crash is happening inside a plugin, the stack trace should show this. Otherwise, we should be able to tell where the crash is actually happening inside the AudioPluginHost.