Well known and really anoying bug. It seems to generate when using the VBA editor and deleting some worksheet that is referenced by some formula.
I have resolved (most of the times) by completely removing the vba project using this procedure:
- Create a backup copy of the file (from file explorer)
- Change file extension from .xlsm to .zip
- Open the .zip file and locate the file
/xl/vbaProject.bin
- Remove this file
- Change the file extension back to .xlsm
- Open normally the modified file. It should not show the error and save without problems
Obviously in this way you will loose all the VBA macros in the Workbook, so you have to re-import them from the last (hopefully) working version of your file.