I have done some more investigation.
All of the files I work with are years old, and created in older versions of InDesign.
I have tried resetting the preferences, I have tried exporting as IDML and reopening. Neither of these worked.
I have located what seems to be the source of the freezing, I have sections in the bottom of the file: 4 appendices and an index, and when I delete these sections the freezing ceases completely. When I try to edit the masters for these sections it freezes again. I think there must be something wrong with the masters, but I do not know what it is.
Are there any known issues with editing documents from previous versions of InDesign that I should be aware of? Or any known settings for these masters I should look into changing to fix this issue with these masters? I would prefer to not delete them and try to recreate them.
