Can't find project or library

[MrDB4Excel]

I have one xlsm file that regularly opens to this message

I have several xlsm files that are in the same folder and references exist between and among these several files but this file is the only one that does this. I have seen other xlsm files in this folder do it but those instance are very rare.
I will fix it by opening an earlier save which opens without giving this message and using the renamed corrupted file update any data in the file that opens without this issue.
The newly saved file works for a while, sometimes a day or two and sometimes like today I fixed it this morning about 7am and just now the fixed file opens to this message.
I have not the vaguest idea why this is happening, any help is much appreciated.

 

[davesexcel]

What code is causing the error?

 

[Norie]

If you goto Tools>References... is anything marked as MISSING?

If there is note it's name, uncheck the item and save the file.

 

[MrDB4Excel]

Thanks to davesexcel and Norie. I discovered per your suggestions one of the sheets contained code that does not belong to this workbook. I deleted the code and now will watch to see how it pans out.