Scrivener has slowed down

Once I got to chapter 10 of my 20 chapter book I noticed that the split at selection (ctrl+k) has slowed down dramatically. It used to be almost instant, and it is in the new document that I hand imported from Snowflake Pro for later writing, but now there is a twenty second lag between the shortcut press before I can edit the title of the new note and resume my scene chopping.

I reset the preferences and changed the fonts back the way I had them, just in case I accidentally enabled something that lags it out but to no avail. It’s still slow.

How can I get the nice speedy Scrivener back that I fell in love with?