[KevinH]

The Double Title Bar is what is really confusing me. Its presence alone is enough to cause the off by one line issue.

It is almost as if there are two main windows nested together. The fact that a fresh start with an empty ini file makes the problem go away for a short time again is quite puzzling.

It is as if something outside of Sigil is confusing the layout and corrupting the ini file.

Or it may be someone changed the mac OS setting that normally limits things to a single gui app running at the same time (ie one instance of Sigil) but allowing multiple main windows for each app.

This is the paradigm used on Mac whereas the other platforms allow multiple instances of Sigil to be running simultaneously.

This looks a bit like two versions of the app melded into one resulting in nested windows.

Either way, something specific to that system is the problem. I am just not sure, what that might be.