Looks like corruption. Run a Recover and see what turns up.
Is the file locally on your computer or is it hosted on the server?
I would start by duplicate the file to keep a safe copy somewhere and then try the following:
- in the file menu you have the option to "save a copy as..." try to create a compacted copy or a clone (no records) and see if the new file still have the issue.
- in the file menu you have a "recover..." option that will allow you to select the broken file and do a consistency check