I don't know how better to describe this issue than as I have in the title. This is just a performance issue, the files are not corrupted or changed. I simply have to save the file and close it and reopen it. All functionality seizes when this happens except for the ability to save with command+S. This is happening every minute or two and making work impossible. I'm running Catalina 10.15.7 on a 2015 iMac with 24GB of RAM.
See attached screenshots for an example of what it is doing.